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 did that for vim word navigation, e.g. `b` to move forward a word. When naming tests I generally treat `_` as a breaker in namespacing.

Probably going to deep on it.