Telemetry - Add Light-telemetry (LTM) support

[magicrub]

Issue request from https://github.com/marksev1 to add LTM for light-weight telemetry at low baud rates. Useful for antenna tracking and critical status at long range. For details, see
cleanflight/cleanflight#36

[marksev1]

Attaching ltm relevant files (its a rar renamed into txt, so I could attach it, please rename file extension):

ltm_2015-11-08.txt

Implementation in cleanflight: cleanflight/cleanflight#1010
Implementation in Taulabs: https://github.com/TauLabs/TauLabs/blob/next/flight/Modules/UAVOLighttelemetryBridge/UAVOLighttelemetryBridge.c

Regarding antenna trackers: Ghettostation supports it and amv-open360tracker also support it (both are on github) and both are massively popular antenna trackers in Germany and Spain with huge following. If you want to use a ground osd based on that telemetry you can use ltm-osd (max7456) to have a redundant ground osd if maybe the one in the plane fails because of loss of video range. Besides apm-planner and mission planner if you want another gcs to display telemetry you can with mwp (github, only for linux, supports ltm).

Taulabs supports it and cleanflight will support it in next release.
Otherwise I'm hoping you guys will like it as much as I and quite a few other people. Hopefully it will get in the codebase.

[auturgy]

Closed by #12158