Refactor/fixes for ProximityRadar and friends

- 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

Rework Fly View into separate layers which can be customized at each layer.