More and Settings

This PR adds:

* Art and Settings cells in the More tab
* A Settings view controller with switches for "Avoid Stairs" and "Hide Art on Map"
* The Settings view controller persists the state of these switches in `NSUserDefaults`, so whenever a user returns to the Settings view, the switches will be set appropriately
* The Settings view controller also contains constants (`MCCSettingsAvoidStairsKey` and `MCCSettingsHideArtKey`) for other classes to use. `MCCClient` can use the first key when getting paths that need to avoid stairs from the server, and `MCCFloorViewController` can use the second key when it needs to know whether to display art markers or not on the map.

This is a bit skeletal, as the Art cell currently leads to nothing, and the Settings view only has two cells, but it's a good start - makes sense to go ahead and merge this into master before we get started on the main items for this build cycle.