#6991 - Add sorting options in the media browser

Redmine ticket: [#6991](https://projects.artefactual.com/issues/6991).

Screenshot:
![screenshot 2014-07-15 at 10 51 44 am](https://cloud.githubusercontent.com/assets/606459/3588925/b96872cc-0c48-11e4-9202-9dbf7456e652.png)