Rewrite parts of the uploads dashboard code

Create UserGalleryApi which inherits from Api, untangle carousel code
(remove the module-global carousel variable).

Change-Id: I15723385d0acce2c3b96511270f74cee34f790f9
Don't load Hogan twice

This slipped in somehow and is wasting bandwidth.

Change-Id: I48b8f958f9851d1786f60a745a454308401329ec
Merge "Rewrite parts of the uploads dashboard code"