Type Lookup/Tootip feature

This adds functionality to lookup information about an identifier under the cursor.  It's similar to a tooltip in Visual Studio.

Some concerns I'd like feedback on:
* The information is printed out to the status line right now.  Maybe it should to go in the preview window instead?
* If this is moved to the preview window, maybe it should display documentation too?
* Would it be worth pursuing a way to add syntax highlighting what's printed?
* I might have gone a little crazy with the unit tests.