Adds API endpoint listing all operator shelves upon which the current user has permission to operate (bug 1074368).

![Mine.](https://cloud.githubusercontent.com/assets/23885/4565352/25abe82e-4f1f-11e4-866f-e56ec9b14b8a.gif)

r? @ngokevin @robhudson @diox 
I like everything you suggested. Tiebreaker to me is that there's a collision in the current situation if you give a shelf the slug of "mine". Edge case, but it's technically correct:

![You are techncially correct...the best kind of correct](http://s2.quickmeme.com/img/62/62f538b129e13afc6c7d9b9278b63f63f4c91e1f8fd1077c36e088039bf538f8.jpg)