service hub component is basically thin layer that deals with converting data to pass in to RemoteWorkspace

Ensure IBC is running for our official builds.

There will be a corresponding update to the Build Definitions to provide the $(IbcMergePath) value.

This prevents the VS and the repository's version of NuGet
fighting over the format of project.lock.json.

Adds two new projects, CscCore and VbcCore, which target CoreCLR and
produce CoreCLR-compatible executables in the core-clr subdirectory of
the build output. At the moment they are not included in any solution
because a bug in the DNX build tools that causes VS 2015 to deadlock
whenever the project files are loaded.

It's confusing for new users to have the Roslyn solutions nested
inside the src/ directory and there's really no good reason those where
there in the first place. This moves them to the root directory, except
for the Toolset.sln solution, which is only for building Roslyn in CI
scenarios and has been moved to the build/ directory.

Need to use forward slashes to be compatible with Unix-like platforms.