Case detail tabs

[Ticket](http://manage.dimagi.com/default.asp?145414)
This feature gives users the ability to organize their case details into tabs. It is behind a feature flag.
![screen shot 2014-11-08 at 8 48 03 am 1](https://cloud.githubusercontent.com/assets/2117127/5165114/0d69120c-73e9-11e4-8379-f6897e76f133.png)
could just be `list(self.get_tabs())`