MUMUP-1170/MUMUP-1185/MUMMNG-886: Filters

Marketplace sort/filter now works. 

You can sort by popularity (currently this means rating, but we could make our own ranking)....
![image](https://cloud.githubusercontent.com/assets/1919535/4467106/33b40ae8-48ec-11e4-995b-c6517234494d.png)

By A-Z....
![image](https://cloud.githubusercontent.com/assets/1919535/4467109/4414c36e-48ec-11e4-847a-93226be93bb7.png)

Or by category....
![image](https://cloud.githubusercontent.com/assets/1919535/4467118/5e8eb38a-48ec-11e4-987b-9b3b5fda3eff.png)


Pretty nifty.