emit a repositoryDeactivated signal when switching the active repository
corrected call order of de-/activated signals in RepoMan
Introduce a new signal that kicks on activation

This new signal is triggered when a transition from NO-Active-Repo to
1-Active-Repo and vice versa happens.
Teach RepoStateWidget to act on deactivation
Merge pull request #4 from macgitver/topic/ImprovedRepoMan

Improvements to repo manager