Support REPOSITION MAVLink command in PX4

-build is much quieter now

Fixed crash when switching to the Flight Modes panel.

Fixing the Mission Editor view to respect the view area

Restoring toolbar transparency.

Offline map

Add GPS drivers and RTCM output for RTK GPS

Tuning not supported on VTOL

This also replaces tabs with spaces

* MavLink/master:
  Fix flight mode display for PX4. Missed reverse channel check

This does the following:
- add RTCMMavlink class that streams RTCM messages via mavlink
- add GPSProvider class that opens a serial device and uses the gps driver
  submodule to get an RTCM stream
- add a GPSManager class that manages the RTCMMavlink & GPSProvider classes
- implement gps driver callback & definitions using Qt
- add the GPSManager to the QGCToolbox

To test this, uncomment the _gpsManager->setupGPS("ttyACM0"); in
QGCToolbox.cc

Fix flight mode display for PX4. Missed reverse channel check

Restore critical messages in the main window.

Fixing transparent "Q" in all icons.

Default case for RADIO_STATUS
In response to #3151.