ArduCopter: alphabetized the contributors list

Jonathan Challinger added
ArduCopter: disable ITERM logging by default

This message takes 1ms to write and we are running over our limits on
some loops.
ArduCopter: update release notes for rc3
ArduCopter: replace FS_THR_RTL_MIN_DISTANCE with wp_radius

This effectively means that an RTL kicked off by a failsafe will
immediately switch to LAND mode only if within 2 meters.  Previously the
radius was much wider (15m).
ArduCopter: smooth throttle when switching from manual throttle to alt hold

new set_accel_throttle_I_from_pilot_throttle function copies the
difference between the pilot's throttle and hover throttle to the
accelerometer based throttle controller's I term.
ArduCopter: bug fix to LAND flight mode not actually landing if initiated from failsafe

An hidden bit of failsafe functionality in the set_mode function was
switching the throttle mode back to THROTTLE_AUTO instead of
THROTTLE_LAND
ArduCopter: move setting of land's yaw mode to the do_land function
ArduCopter: update firmware version to 2.9-rc4
ArduCopter: updated release notes for 2.9-rc4
Copter: relax altitude check in verify_takeoff

Previously we checked if the alt > target_alt but because there is
little to no overshoot with the new accel based alt controller this
check was failing for some users.
Copter: added experimental LOITER_REPOSITIONING #define to config.h

APM_Config.h should be used to overriding the standard parameters but
they still require a definition in config.h or they will be undefined
when built by the mission planner.
Copter: constrain loiter so that it never commands more than 45 degrees of lean in lat or lon directions
Copter: added CH7 switch to enabling/disable the sonar in flight

This indirectly switches surface tracking on/off which is useful to
avoid tracking the tops of uneven objects when far above the ground
Copter: constrain auto roll and pitch to 45 degrees
Copter: update firmware version to rc5
Copter: bug fix to altitude check of verify takeoff

set_next_WP function was not setting the alt_change_flag properly
Copter: RTL bug fix to initial step is always a climb and not a descent

Also bug fix to hold yaw on take-off
Copter: update firmware version to 2.9 ahead of release