Added parameter RALLY_TOTAL.
Added handlers for new MAVLink messages RALLY_POINT and
RALLY_FETCH_POINT.
defines.h modified to make room in EEPROM to store rally points.
rally.pde added and is responsible for ensuring rally points get
stored in the correct spot in EEPROM.
Multiple Rally/RTL point support now done. If rally points have
been defined, then when RTL mode is entered, the closest Rally
point is chosend and the plane loiters at that point.
Note only 10 rally points can be defined; this is to save space in
the APM's EEPROM.
Andrew Tridgell
Michael Day