Made reference assembly lookup work on 32bit machines

#221
Added double check lock to NetPortableProfileTable
- Package restore has a race condition where this could be null
Fixed path matching bug
- Make sure paths have trailing slashing before comparing
- Added unit tests
- Modified makefile to run test on the new runtime instead of the old one.
  This makes it possible to do *any* testing.
Clean up leaky compiler options abstraction
- Changed compiler options to be a model type in Microsoft.Framework.Runtime.
- GetCompilationSettings converts those generic values into Roslyn CompilatonOptions.
- Enabled Microsoft.Framework.Runtime.Roslyn.Tests project
- Added a bunch of tests for project parsing
Added header