Parachute: initial draft library
RC_Channel: add parachute_release to function enum
AP_Parachute: add example sketch

Only tests that the lib compiles
Copter: integrate parachute lib
Copter: extend crash check to trigger parachute
Copter: ch7/ch8 parachute release
AC_AttControl: return angle_ef_targets as const ref
Copter: add min alt check to parachute release
GCS_MAVLink: add MAV_CMD_DO_PARACHUTE
GCS_MAVLink: generate after MAV_CMD_DO_PARACHUTE added
Mission: add support for MAV_CMD_DO_PARACHUTE
Copter: process MAV_CMD_DO_PARACHUTE commands
Parachute: minor comment changes
Copter: log parachute events
Notify: add parachute release tune for Pixhawk
Parachute: set AP_Notify parachute_release flag
Parachute: add AP_Notify.h to example sketch
Parachute: add 0.5sec delay before parachute is released

This allows a short warning to the user through the new parachute_release tone
AutoTest: make sim_arducopter_randy.sh executable
AC_AttControl: increase default rp accel to 900deg/s/s