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
Drop VsCommon in namespace

(because that's an internal namespace)
Merge pull request #629 from pmiossec/cleaning_after_vs2008_support_removed

Cleaning after vs2008 support removed