Enable/Disable based on fixed base position

Add support for specifying fixed RTK base position

Added support for qgcRebootRequired Fact meta data value.

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

Add new Help page under Settings

Show the link indicator in the tool bar if two or more links are connected and at least one of them is a high latency link.
Show in the link indicator if a link is inactive.

This setting enables/disables the LinkIndicator toolbar in which the primary link can be chosen.

Automated preflight checklist: Initial commit. Note that this requires an autopilot firmware that writes the respective health flags in the SYS_STATUS mavlink message

All settings wired and persistent
Cleanup non Airmap builds

Moved "Grid Lines" out of General Options and into the Video Stream Widget
Made a QGC custom Switch element

Added AirMap settings (SettingsGroup)
Added AirMap settings block to General Settings
Create macros to deal with the tedious repetitions within SettingsGroup
Removed old, hacked in setting for AirMapKey
Remove a few of the tons of build warnings

This reverts commit 52160d80.