Switch to using mapquest tiles

Summary:
- Use cloudmade tiles for main map and location form widget.
- Add aerial map layer, and include in layer control
- Add layer control to location form widget
- Add map data and imagery notes to LICENSE.md

Closes T96

Test Plan:
- Load homepage. See MapQuest map layer
- Click the layer icon on the map, select "MapQuest Aerial". See Aerial map tiles load.
- Click create post, pick a form, see that the location picker now uses MapQuest layers.
- Also note the location picker now has a layer switcher control too.

Reviewers: shadowhand, eyedol

Reviewed By: eyedol

Maniphest Tasks: T96

Differential Revision: https://phabricator.ushahidi.com/D24