Adding panels for trove

* Add python-troveclient to requirements.
* Add trove api to openstack_dashboard apis.
* Add Database Instances panel.
* Add Database Backups panel.

Implements: Blueprint trove-support

Change-Id: I0541534612ccb491d692168c3c9ca7a841650be6
Adding tests for databases and database_backups
Merge pull request #2 from crazymac/trove

Trove. Adding tests to trove branch