Remove unused code

- add NOTIFY for distanceSensor property
- add DistanceSensorReadingsChange() callback prototype

- revert excessive NOTIFY
- adding MaxSensor into DistanceSensor frame handling

- add proximity radar view in map view
- add proximity radar view in video view

change distance label positioning in video view

clean up unwanted comments

- space up proximity sectors
- revert unwanted changes in qgroundcontrol.qrc

squashed commits

Unified photo/video control which works with mavlink cameras and just video stream

Support for reusable InstrumentValueArea control

Refactor instrument value controls

Allow split of current segment

New MapLineArrow control