Plane: add support for DO_SET_ROI within mission
Rover: add support for DO_SET_ROI within mission
Rover: add support for DO_SET_ROI outside of missions
Plane: add support for DO_SET_ROI outside of missions
documentation: Add a contributing & maintainers file

Per our devcall last week.  Adding now mainly so we can start pointing
LogAnalyzer fixes to @chapman and quickly get them into master.

@tridge & @randy - I kinda guessed at the maintainers list, we can
update later as needed.
all: Change the editorconfig so that it won't want to reformat

.editorconfig is a great way to ensure developers follow our
line ending/tab conventions, but we shouldn't have it default
to fixing any lines that were not edited.
Copter: Ch7/8 option to retract mount

-Define AUX_SWITCH_RETRACT_MOUNT in defines.h
-Added 27=Retract Mount to Parameters.pde CH7 and CH8
-added int on CH7/8opt AUX_SWITCH_RETRACT_MOUNT
-Added Case #if Mount == ENABLE to set mount mode
made set_mode public in AP_Mount.h lib
Mount: set_mode method made public