Cloning reliability improvements 

Tested in VS2010 against TFS 2012. Tested multiple repositories, including vary large projects with lots of previous branching. Code submitted following manual testing and multiple runs without warnings. Discovered a load/timing issue around the high frequency of create then delete workspace that was triggering exceptions and reliability issues for existing users. Applied changes to the *workplace.delete()* to *Retry.Do* with large time lag (5 seconds) to help allow the TFS server to finish tasks before trying again. I suspect that TFS makes the assumption that workspace changes are infrequent and hence should be low priority threading.
It wasn't clear if calls to the TFS workspace.Refresh method might mitigate the issue as well.