Add implicit restore when running analysis. Adds --no-restore option.

[JoeRobich]

Resolves #848

Example output:

  The dotnet format version is '5.1.0-dev'.
  The dotnet runtime version is '6.0.0-alpha.1.21064.11'.
  The dotnet CLI version is '6.0.100-alpha.1.21065.7'.
  Using MSBuild.exe located in '/usr/local/share/dotnet/sdk/6.0.100-alpha.1.21065.7/'.
  Formatting code files in workspace '/Users/joeyrobichaud/Source/format/format.sln'.
  Loading workspace.
    Determining projects to restore...
  Restored /Users/joeyrobichaud/Source/format/perf/dotnet-format.Performance.csproj (in 2.38 sec).
  Restored /Users/joeyrobichaud/Source/format/tests/dotnet-format.UnitTests.csproj (in 3.24 sec).
  1 of 3 projects are up-to-date for restore.
  Project dotnet-format is using configuration from '/Users/joeyrobichaud/Source/format/.editorconfig'.
  Project dotnet-format.UnitTests is using configuration from '/Users/joeyrobichaud/Source/format/artifacts/obj/dotnet-format.UnitTests/Debug/netcoreapp2.1/dotnet-format.UnitTests.GeneratedMSBuildEditorConfig.editorconfig'.
  Project dotnet-format.UnitTests is using configuration from '/Users/joeyrobichaud/Source/format/.editorconfig'.
  Project dotnet-format.Performance is using configuration from '/Users/joeyrobichaud/Source/format/.editorconfig'.
  Complete in 12984ms.
  Determining formattable files.
  Complete in 1885ms.
  Running formatters.
  src/Utilities/DotNetHelper.cs(1,1): Fix file encoding.
  Running Code Style analysis.
  Determining diagnostics...
  Running 22 analyzers on dotnet-format.
  Running 22 analyzers on dotnet-format.UnitTests.
  Running 22 analyzers on dotnet-format.Performance.
  Complete in 27582ms.
  Analysis complete in 27583ms.
  Complete in 29067ms.
  Formatted code file '/Users/joeyrobichaud/Source/format/src/Utilities/DotNetHelper.cs'.
  Formatted 1 of 98 files.
  Format complete in 43937ms.