Added original Microsoft ReferenceSource classes

I've replaced the UnityMVVM classes with the original Microsoft ReferenceSource classes. Also included are the required attributes and dummy classes.

The MVVM classes are taken from this repository:
https://github.com/Microsoft/referencesource/

DummySR contains a subset of error messages for the included classes.

DummyUserControl is a replacement of System.Windows.Controls.UserControl
for NoesisGUI.