Enable S.BUS TX pin
Build test code for S.BUS output, send test characters once S.BUS1 or S.BUS2 is enabled
test loop
Fix quotation marks
Turn off JTAG completely in a vain attempt to get PB4 free for SBUS enable.
Be more enthusiastic with the sbus enable pin. Still no love.
Don't leave all JTAG off... it will make you very sad
Remove the s.bus test loop... makes it very hard to update the firmware.
Make SBUS output exclusive
Ensure only either S.BUS1 or S.BUS2 can be active at a time
navigator: RTL: set loiter wp instead of normal waypoint in RTL_STATE_DESCEND
navigator: RTL: set normal waypoint instead of takeoff waypoint in RTL_STATE_CLIMB
Use single set of arm/disarm code

Set mode and arm/disarm commands now call a single method to arm
disarm, thus removing code duplication. Also calls updated
arming_state_transition method such that the arming state logic does
not need to be duplicated outside of arming_state_transition.
arming_state_transition now outputs error messages

If mavlink fd is passed in method will output reason for arming failure
to mavlink.
Function naming and remove unneeded sprintf
geo lib: major rewrite of map_projection_XXX functions
Use updated map_projection_XXX functions in apps
mc_pos_control: operate in local projection instead of global frame
position_estimator_inav: mark local position as valid even if GPS not available (e.g. only FLOW)
geo lib: minor code style fix