Add edit terms permission for overridden permissions and roles vsites.

#5694
![epod directors evidence for policy design](https://cloud.githubusercontent.com/assets/1222368/2575810/8a5a2888-b95d-11e3-9acd-814753fe3ce6.png)
![manage members evidence for policy design](https://cloud.githubusercontent.com/assets/1222368/2575811/8a5d52b0-b95d-11e3-8af8-6f342e7649c5.png)
@amitaibu @Ferdi We would probably need an upgrade path and tests for that, right?