Add ability to disable/deactivate repository

It would be nice to have the ability to disable repository configuration in Bamboo. Similar to what Fisheye & Crucible does where you can stop/start the repository. Bamboo uses a polling mechanism for branch/change detection, and it would be a good idea to have a switch where you can turn ON/OFF the repository whether it's a Linked repository or plan-level repository, so you can easily deactivate it instead of having to delete it if you want to temporarily prevent people from using that configuration, and also to ensure that none of Bamboo's background processes will run for that repository.