Add support for scanning exception regions

[vitek-karas]

Valid once #16 is merged.

Repro:
Update the repro program by changing Main to contain try/catch/finally and calling some new methods from the catch and finally regions.

Fix:

• Work is done in MethodBodyNode.cs
• Use bodyBlock.ExceptionRegions to get to the exception regions in the original method
• Update GetStaticDependencies to report the catch clause type token dependency
• Include exception regions when rewriting the method body in Write.
  • The code already uses InstructionEncoder so just add a ControlFlowBuilder to it
  • Use the ControlFlowBuilder to add labels for the try/catch/finally blocks
  • Add exception regions
  • Remap the catch clause type tokens

Don't forget (or add an issue for) about filter blocks.