Refactored PX4 radio config to work with both PX4 and APM

APM Mission fixes

Show altitude in mission item

Fix altitude relative to home default

Standalone coordinate support for mission items

Standalone coordinate don’t connect to waypoint lines

Simpler this way

Show altitude difference from prev waypoint in editor

Standalone coordinate don’t connect to waypoint lines

Simpler this way

Acceptance radius fixes

Disconnect inactive links

Both altitude and acceptance radius will track last value

Add mission item categories

- New mission command editor dialog
- New MissionCommands toolbox object to get command info
- Added APM mission item set

Mobile tweaks

Add support for v4 boards

Enable binding mode commands to joystick buttons

Remove qgcvideo

Completed Link Configuration Settings

* MavLink/master:
  Friendly edit for APM supported mission item