…tead of crashing on non-messages.

This fixes a crash for me on cargo 0.19.0 (28d1d60d4 2017-05-16), example output follows:

I:\home\projects\test\testrust>cargo build --message-format=json 2>NUL
{"features":["default","use_std"],"filenames":["I:\\home\\projects\\test\\testrust\\target\\debug\\deps\\liblibc-f4ccf2fa58092d85.rlib"],"fresh":true,"package_id":"libc 0.2.24 (registry+https://github.com/rust-lang/crates.io-index)","profile":{"debug_assertions":true,"debuginfo":2,"opt_level":"0","overflow_checks":true,"test":false},"reason":"compiler-artifact","target":{"crate_types":["lib"],"kind":["lib"],"name":"libc","src_path":"C:\\Users\\MikeR\\.cargo\\registry\\src\\github.com-1ecc6299db9ec823\\libc-0.2.24\\src\\lib.rs"}}
{"features":[],"filenames":["I:\\home\\projects\\test\\testrust\\target\\debug\\deps\\librand-76456d761c2cb637.rlib"],"fresh":true,"package_id":"rand 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)","profile":{"debug_assertions":true,"debuginfo":2,"opt_level":"0","overflow_checks":true,"test":false},"reason":"compiler-artifact","target":{"crate_types":["lib"],"kind":["lib"],"name":"rand","src_path":"C:\\Users\\MikeR\\.cargo\\registry\\src\\github.com-1ecc6299db9ec823\\rand-0.3.15\\src\\lib.rs"}}
{"message":{"children":[],"code":{"code":"E0425","explanation":"\nAn unresolved name was used.\n\nErroneous code examples:\n\n```compile_fail,E0425\nsomething_that_doesnt_exist::foo;\n// error: unresolved name `something_that_doesnt_exist::foo`\n\n// or:\n\ntrait Foo {\n    fn bar() {\n        Self; // error: unresolved name `Self`\n    }\n}\n\n// or:\n\nlet x = unknown_variable;  // error: unresolved name `unknown_variable`\n```\n\nPlease verify that the name wasn't misspelled and ensure that the\nidentifier being referred to is valid for the given situation. Example:\n\n```\nenum something_that_does_exist {\n    Foo,\n}\n```\n\nOr:\n\n```\nmod something_that_does_exist {\n    pub static foo : i32 = 0i32;\n}\n\nsomething_that_does_exist::foo; // ok!\n```\n\nOr:\n\n```\nlet unknown_variable = 12u32;\nlet x = unknown_variable; // ok!\n```\n\nIf the item is not defined in the current module, it must be imported using a\n`use` statement, like so:\n\n```ignore\nuse foo::bar;\nbar();\n```\n\nIf the item you are importing is not defined in some super-module of the\ncurrent module, then it must also be declared as public (e.g., `pub fn`).\n"},"level":"error","message":"cannot find value `guess_no2` in this scope","rendered":null,"spans":[{"byte_end":604,"byte_start":595,"column_end":23,"column_start":14,"expansion":null,"file_name":"src\\main.rs","is_primary":true,"label":"did you mean `guess_no`?","line_end":24,"line_start":24,"suggested_replacement":null,"text":[{"highlight_end":23,"highlight_start":14,"text":"\t\t\t\t\tif      guess_no2 < target { println!(\"Guess too low\"); }"}]}]},"package_id":"testrust 0.1.0 (path+file:///I:/home/projects/test/testrust)","reason":"compiler-message","target":{"crate_types":["bin"],"kind":["bin"],"name":"testrust","src_path":"I:\\home\\projects\\test\\testrust\\src\\main.rs"}}
{"message":{"children":[],"code":null,"level":"error","message":"aborting due to previous error","rendered":null,"spans":[]},"package_id":"testrust 0.1.0 (path+file:///I:/home/projects/test/testrust)","reason":"compiler-message","target":{"crate_types":["bin"],"kind":["bin"],"name":"testrust","src_path":"I:\\home\\projects\\test\\testrust\\src\\main.rs"}}

…dd them to Release vsix builds.

I've observed that in practice this allows the completion of basic static methods, such as "rand::thread_rng().gen_range(1,11);"

… directory.

This was presumably originally done to improve "racer find-definition"'s results.
However, it takes an optional [substitute_file] parameter we can use instead:
    racer find-definition <linenum> <charnum> <path> [substitute_file]

This change eliminates the following churn in the "Visual Rust" output tab:
    Apply change: File created: I:\home\projects\test\testrust\src\main.rs~RFa2df0b.TMP
    Apply change: File created: I:\home\projects\test\testrust\src\main.rs~RFa2df0b.TMP
    Failed to apply change 'File created: I:\home\projects\test\testrust\src\main.rs~RFa2df0b.TMP':System.ComponentModel.Win32Exception (0x80004005): Access is denied
       at VisualRust.ProjectSystem.FileSystem.ToShortPath(String path)
       at ...
    Apply recovery change: Directory created: I:\home\projects\test\testrust\

…ion s caused by spurious readonly.

Errors in macro expansions sometimes don't have real "file_name"s at every expansion level.
This simply attempts to recursively expand until we can combine the paths sanely.
Other alternatives might include comparing against target src_path, or looking for an ".rs" extension.

- Will make parsing available to future "signature help" popup hints.
- Handle unescaping of rust strings, semicolon escapes, etc.
- Document the heck out of members, complete with examples.

User Interface changes:
- F1 Help can now look up types, primitives.
- Find definition now fully delegates to 'racer find-defition'.
- Rust completions no longer triggered when definining new identifiers.

Tokenization changes:
- Replaced misused/understood "GetTokensAtPosition" with "GetLineTokensUpTo" and "GetTokensAt".
- Documented and added explicit examples to help head off any confusion.
- Added tracing of RustCompletionCommandHandler to see impacts.

Fixed problems / rationale:
- Single character tokens could previously never be "currentToken".
- "currentToken" was usually null.
- "leftToken" would often be the *last* token when typing in the *middle* of a line.

Possible future paths:
- Some kind of multiline token fetcher that fetches enough tokens for us to work with, without tokenizing the entire document.
- Full blown AST?

Previously, all documentation for an identifier was displayed.  This
included "# Examples" sections and lots of potentially long and rambling
documentation.

Rustdoc conventions suggest an initial "summary line", which would be
a good defacto standard to display.  In practice, the initial few
paragraphs before the first header section also seem worth displaying,
but that's perhaps more my personal taste.  I've provided accessors for
getting at "Plain" versions of both.

Refactoring:
- RustCompletionSource:  Move regexps to RacerMatch.
- RacerMatch:  Expose Plain{Documentation,SummaryLine,SummaryParagraphs}

Floating point numbers aren't considered STRUCTURAL, so this doesn't
incorrectly trigger for "12." and similar expressions.

The default errors that e.g. Visual Studio gives when failing to do
either of these are unhelpful at best, downright confusing at worst.
As I'm apparently not alone in overlooking these steps, they seem worth
documenting.

Ref: PistonDevelopers#294
     "Multiple Issues opening and building the solution in VS2017"

…017 build.

Also build Debug platforms for completeness.

Configurations:
  - Removed "Debug.Lab" and "Release.Lab" - these seem unnecessary.
  - Always build 'everything', instead of a weird hodge podge of missing
    projects for any given configuration.
  - Always build project configurations by the same name.

Platforms:
  - "Mixed Platforms" replaced with "All VS", which builds everything always.
  - New "VS2015 Only" builds everything but VS2017-specific projects.
  - New "VS2017 Only" builds everything but VS2015-specific projects.
  - "x86", "x64", and "Any CPU" are all removed.  We always want to build
    a mixture of "Any CPU" (most projects) and "x86" (setup projects.)

Closes PistonDevelopers#295
       "Clean up solution config/platform matrix."

.debug.vsixmanifest already referenced LICENSE.txt

Ref: PistonDevelopers#301
    "Could not uninstall VSIX - looking for LICENSE.txt"