Add authorized attribute to enrollment

To check if the enrollment has been authorized by the campaign owner
Add translation strings for joining campaigns
Move joined_campaigns view to its own partial

* Adds a enrollment authorization status label on that view
Shallow routes for campaigns & enrollments

Change joined_campaigns path to recruitments_user_path
Change joined_users path to recruits_campaign_path

Both changes were made to avoid confusion with enrollment paths
Campaign owner may authorize or reject requests to join
Merge pull request #15 from Intngbl/bouncer

Bouncer