Set RevitDynamoModel and create test scheduler.

This pull request fixes DynamoRevitTest to be used with the scheduler. When testing, the dynamo model must be created with a scheduler that does not rely on Revit's idling event because RTF never returns control to the application. In addition, the RevitDynamoModel property needs to be set to avoid null reference exceptions during later initializations.

Requires Merge:

- [ ] Revit2015

PTAL:
@Benglin