Camera tracking

This maps the TabletInfo position to the POILocation (when TabletInfo.Mode = CameraPOI) and adds a POI mode for the yaw axis which will make it face that object. Also the pitch axis of a gimbal will track it.

Tested the yaw functionality on a non-gimbal quad and it worked well although there are about 5 meters of error between tablet GPS and UBX.

Push against james/development