DNM:  Begin separation of CoreNodes into WPF specific library

### Notes

There are still lingering references of WPF in CoreNodesUI that require special effort to separate.

### Outstanding sub-tasks

* WatchViewModel should not live in the Model layer http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-5633
* Remove System.Windows.Controls reference in WatchImageCore http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-5634