Adjusted icons so they no longer contain a background.
Added *Exclusive* functionality to the RoundButton element.
Added OnClicked signal for the drop down boxes so I could turn off Add Mission Item and Home Mode.

Made then the same size of toolbar cell height

Also moving the Plan View tool bar buttons into a Row element.

- select active vehicle
- arm/disarm
- select flight mode

Tweaking MapType and MapCenter icons
Added Zoom Plus/Minus icons to be used for maps
Added PiP icon for the upcoming Picture-in-Picture functionality

Also:
- Remove unused code

Use import QGroundControl 1.0 to get to it

Also much other cleanup/change

This allows for testing issues found on high dpi screen without needing
a high dpi screen. it does this by doubling the font sizes.

Plus more overall ui work

- New MissionManager
- Plumb MissionManager through MissionEditor
- Mission Editor supports get/set

- Restructured a number of MissionItem properties as well

Plus lots of other cleanup

- MultiVehicleManager is a Qml friendly replacement for UASManager
- Vehicle is a replacement for both UAS and AutoPilotPlugin