Fixes https://github.com/aspnet/KRuntime/issues/910

@Chengtian @muratg
Servicing work in progress
Servicing file format update

Changing key=value delimiter to =
Long path redux
- Rely on FilesChanged to trigger new compilations
- Removed most of the directory watching code from roslyn compilations

#961
Fixed regression on mono

- Use HOME instead of ProgramFiles
- Removed tracing for replacement attempts
#974
Made some changes to how DTH sees wrapped projects
- Fix up the dependencies list when returning wrapped csproj and
assemblies.
- Changed how unresolved dependencies were implemented. This allows
a specific IDependencyProvider to say a dependency is resolved, but mark
it as unresolved so that fallback does not happen.
- Remove special logic from the UnresolvedDependencyProvider and made it
a first class property on LibraryDescription.
- Mark projects as unresolved if they do not have a compatible target framework
#945
Preserve original project.json paths in DTH
- Added new WrappedProjectPath to the ProjectReference message. This
allows us to preserve all information so that editors can watch the
relevant project.json and wrapped project.
Tweaked unresolved project logic
- Mark projects as unresolved only if frameworks are specified
and none of them match.
Wrap project compiling in child assembly load context