fix crash due to result existing both in compiler and ide side.

Add an internal CompletionItemRules.Create that still uses a boolean to ensure binary compat with typescript

Fix tests

Add a public "MatchPriority" class that defines 2 possible values.

It's contained in the diagnostics window VSIX, which we include in
the full deployment.

* initial port from CSharpEssentials

* responding to feedback.
removing syntax rewriter and incorporating formatting rules into formatter

* responding to cryus' feedback

- general logic cleanup
- moving methods to abstract base class

* initial port from CSharpEssentials

* responding to feedback.
removing syntax rewriter and incorporating formatting rules into formatter

* responding to cryus' feedback

- general logic cleanup
- moving methods to abstract base class