Move installed/purchased/developed lists in a separate 'apps' key (bug 969433)

This will make the consumer side a little easier to implement, and
since it's private API nobody is using yet we can do it without
fear of breaking backwards-compatibility.
Merge pull request #1794 from diox/api-return-apps-in-dict

Move installed/purchased/developed lists in a separate 'apps' key (bug 969433)