Massive overhaul of grammar

[damieng]

Ideally this would have been smaller changes but the grammar had many many issues.

This adds support to or fixes highlighting for:

• Generic methods
• Generic types
• Type constraints
• Extern fields
• Nullable/pointer built-in types
• Lambda method syntax (C# 6)
• Method bodies
• Type recognition on cast/as/in/sizeof/typeof
• Interface names (convention based on I[A-Z] in absence of type engine)
• Improvements in newline handling (allowing more, not requiring any)

Ideally would have more work done on newlines and comments being allowed everywhere but that's an ongoing issue.

Here's what code can now look like using a VS-style theme I put together;

Still remaining before merge:

1. Fix specs
2. Get basic types parsing in method bodies