Switch to using firmware manifest for ArduPilot flashing

Offline Maps: Allow custom build settings overrides

ArduPilot for configurable mavlink stream rates

Expose guided altitude settings. Rearrange Fly and Plan view settings.

Move all airmap related stuff to its own directory

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

* Map type now set from General settings
* No map type control in maps