Added support for qgcRebootRequired Fact meta data value.

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

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.

Just use settings defaults

Instead of hardcoded "QGroundContorl" strings

No more user prompting

Convert bool settings to SettingsFact

* Holds all the settings for the app
* Allows core plugin to override default values

- Shot Interval in Survey
- Much change to time/distance calc