Scan method body for dependencies

[vitek-karas]

Scan method body instructions for all opcodes which take a token operand.
Create static dependency nodes for all tokens found.
Rewrite the method body when writing output to update all tokens in it.

I improved the tests to validate member removal as well.

Implementation notes:

• Brings in ILReader and ILOpcode form the type system
• For now implemented ThrowHelper stub since the type system code uses this.

What's missing:
Scanning exception regions and reporting dependencies for tokens in them
Rewriting exception regions and updating tokens in them
I added #17 to track that work.

[MichalStrehovsky]

Looks good otherwise!