add TextMate engine and .vsix import

[lextm]

1. Allow SharpIDE to import existing VS for Windows .vsix files, but limit the imported items to just TextMate based syntax file now. (T4Language.vsix for example)
2. Add TextMate syntax highlighting engine to code editor. (T4 highlighting, include C#/VB.NET best effort detection)
3. Allow SharpIDE to create generic files with language specific extensions based on the imported language specification. (.tt and others)
4. Add a prototype UI in Settings to manage imported extensions

I agree to the terms of contributing as stated here