Add CI for release/uwp6.0 branches of coreclr and corefx (#733)
Add CI for release/uwp6.0 branches of coreclr and corefx (#733)

* Add CI for release/uwp6.0 branches of coreclr and corefx

* Add CI for wcf and core-setup release/uwp6.0 branches

* Add ability to run helix test infra for corefx release/uwp6.0

mmitche/dotnet-ci,dotnet/dotnet-ci,tannergooding/dotnet-ci,dotnet/dotnet-ci,tannergooding/dotnet-ci,mmitche/dotnet-ci