Change obsolete method to authenticate to a TFS Server
Refactoring
Remove unneeded packages
Invoke asynchronously OnActivate to prevent from canceling later events.

Later events are canceled when UI components' state is being changed. (Here: statusStrip.Hide();)
Closes #2397.
Merge pull request #2414 from pmiossec/update_tfs_authentication

Update tfs authentication
Remove an uneeded refrence that cause a warning
Merge pull request #2415 from pmiossec/remove_uneeded_reference

Remove an uneeded reference that cause a warning