Use correct terminology for Altitude values

Option driven firmware version check

Fix flag checks

Heading to Home on Vehicle FactGroup

Add Distance to GCS to Vehicle FactGroup

This reverts commit c69a49e6.

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

FirmwarePlugin: Issue a warning upon connecting if the firmware in use is not using a stable release

Add support for specifying fixed RTK base position

Fix critical check

PX4 prearm checks severity

Change to case insensitive compare

Move ArduPilot preflight check handling to generic QGC

Fixed the core MAVLink receiver. Among other things, it wasn't accounting for fragmented messages.
Fixed code that monitors messages received (and lost)
Added a section within the MAVLink panel to show the current status (for the current vehicle)
Remove some old, unused exposed interfaces

Also fixing some c++ errors within commented off code as the localization engine was getting confused by it.

Fix negative wind direction