Make preprocessors actually work on CoreCLR
- Introduced IAssemblyNeutralInterfaceCache interface since we need
these to be loaded once per app domain. All child load contexts
need to use ANIs that have already been loaded earlier.
- Enhance fallback loader logic so that it takes host loaded assemblies
into account for child loaders.

#829
Removed unused accessor
Updated to the new TFM
Add default Win32 resource when emit assembly

This change will enable the proper information be showed in file property
through Windows Explorer
Add all sub directories as a cache dependency
- In VS adding an empty folder then adding a file
doesn't bust the cache.
Merge branch 'release' into dev
Added package descriptions
Merge branch 'release' into dev