[TIMOB-1493] iOS: MapView user interaction disabled when removing event listener

If you attach an event listener to a MapView and then remove it, the MapView will stay frozen, e.g. no user interaction will be possible.

To reproduce the problem, run the attached app.js file and try this:

1. Click the "Add listener" button
   
2. Note you can move and pinch the map
   
3. Click the "Remove listener" button
   
4. MapView "freezes", you are not able to move or pinch the map.

The issue seems to come from handleListenerRemovedWithEvent in TiUIView.m, specifically this part:

self.userInteractionEnabled = NO;
self.multipleTouchEnabled = NO;

User interaction should probably stay enabled with MapView even when there aren't any touch event listeners attached.