Fix for sketches script usage in checker options

Reduced blocking timeouts in the UI to 250ms and full block to 5000ms.

Fix for nested lambda tooltips not showing if they were generic
functions.

Refactored some common symbol parsing code so it can be reused rather
than copied.
Some sleight of hand to ensure the F# lexer doesnt throw when the script extension is not fsx, we need sketchfs files to be red by the lexer, syntactically they are identical, albeit treated differently via the mime type handlers in Xamarin Studio.