Geodetic reference: Corrected firmware to use mean seal level altitude.
Note, the tablet altitude needs to be resolved.
Geodetic reference: Clarified text box instructions.
Failsafe: only enable stabilization when armed

If the system is disarmed when failsafe is engaged disable all
stabilization to make sure control surfaces do not respond. This
means a transmitter is required now to test the and tune the gains
on a fixed wing.
KMLExport: Added airspeed to export map. Also changed timespans to work on
flight path lines, making it easier to follow the vehicle's trajectory.
[KML export]: Changes requested in review.
ManualControlCommand: use named channels

The channels field of ManualControlCommand has mapped to named
channels for quite some while but the fact it just shows us as
a vector lead people to believe it was related to the order of
the underlying driver layer.  This should decrease that
ambiguity.
Merge pull request #916 from peabody124/manual_named

ManualControlCommand: use named channels
Merge pull request #851 from kubark42/fix-geoidseparation

Fix geoidseparation
Failsafe: when tablet has error, reset failsafe controller

If the tablet mode fails for some reason and we fall back to the
failsafe controller, it should be correctly told when it is a new
execution.
Merge pull request #877 from peabody124/fs_armed

Failsafe: only enable stabilization when armed
TabletControl: do not segfault if PathDesired not initialized
ManualControl: remove unused block of code

This conditional was never triggered since CC defines
PIOS_MANUAL_STACK_SIZE
but it was misleading since it read like it was used.
Merge pull request #928 from peabody124/remove_unused

ManualControl: remove unused block of code
Merge pull request #929 from peabody124/tablet_nocrash

TabletControl: do not segfault if PathDesired not initialized
Merge pull request #846 from kubark42/kml-add-airspeed

KMLExport: Added airspeed to export map