Make an "unresolved" option

[edmundedgar]

Contracts may want to distinguish their handling of "unresolved" from their handling of "invalid". This can happen when you have a question about an event that's only relevant when the event happens, and we don't know when that will be, but you still need the "invalid" option for when the question doesn't make sense, the game was cancelled etc etc.

Probably do something like:

• Add an optional parameter to the question JSON something like "has_invalid" and make new templates like the original built-in templates, but with this option turned on
• Assign 0xffff..fffe as meaning "unresolved"
• Anywhere in the UI where we have an "invalid" option, make a similar UI for "unresolved", provided the option is on.