Move sets into a sub-app

Summary:
Move sets list and detail view into a subapp.

Note some of the styling on sets detail view is already broken.

Ref T347

Test Plan:
- Enabled sets view
- Go to sets list and check it loads
- Go to a set detail page - check this loads

Reviewers: eyedol, shadowhand

Reviewed By: shadowhand

Maniphest Tasks: T347

Differential Revision: https://phabricator.ushahidi.com/D194