preload candidates listing on makeshift operator dashboard (bug 907401)

For Operators to view which apps have opted-in for preloading with FxOS devices.

- A barebones v1 implementation to kick the preloading project, will probably end up using Commonplace and APIs
- Creates a page with a bare-bones listing opted-in preload candidate apps.
- Created an operators app for it to live on.
- Rename preinstall => preload
- Gave the Operators group their own permission (Operators:*)

![screen shot 2013-10-22 at 6 22 47 pm](https://f.cloud.github.com/assets/674727/1386916/a5dab6d6-3b81-11e3-9752-1facca141cd7.png)