Merge pull request #626 from pmiossec/fetch_by_lots

[Need Tests] Fetch by lots
Merge back TfsHelper.PostVs2010.Common.cs in TfsHelper.Common.cs
Bring back all the TFS common code in TfsHelper.Common.cs (DRY!)
TfsPlugin is the same for all versions...
WrapperForWorkspace and WrapperForBranchObject could go in Wrappers.cs
Simplify a little more registry read for VS>=2012