Refactoring GetLibraryExport
- Make each call to GetLibraryExport only resolve direct exports
- Walk the resolved dependency tree using the ILibraryManager
 to resolve transitive metadata references.
- Remove UnresolvedMetadataReference as it's no longer needed
More clean up
- Clean up logic in NuGetDependencyResolver to use the target framework
 passed into GetLibraryExport
- Resolve references inline
Added GetAllExports to ILibraryManager
- Reused ProjectExportProviderHelper for both ILibraryManager and
  ProjectLibraryExportProvider
Fixed build and design time host
- Changed ProjectBuilder and ProjectMetadataProvider to use
  ILibraryManager instead of ILibraryExport directly.
De-dupe source references
Small fixes and tweaks due to recursive roll up
- Use ILibraryManager for ProjectAssemblyLoader
- Change DFS to a BFS so we can look at dependencies in level order
- Only export source files from the top level
Initial changes to make kpm restore work on core clr
- Still doesn't support reading or writing private sources
- Still doesn't support proxies
Make "kpm restore" runnable on CoreCLR

- Copy essential dlls into KRE package manager dependency folder
- Resolve exception caused by multiple async readers/writers working on one
  DefalteStream
- Add support for basic authenticated proxy
Fixed the cache key for the the ProjectLibraryExportProvider
- Use the name, target framework and configuration