Plane: raise default LIM_PITCH_MAX to 20 degrees

15 is often not enough to climb
HAL_PX4: switch to new serial port for 2nd GPS
AC_AttControl: Stabilize input shaping
Copter: integrate AttControl input shaping
AC_AttControl: smoothing_gain to angle_ef_roll_pitch_rate_ef_yaw_smooth

pair-programmed with lthall
Copter: integrate AttControl feel param
Copter: replace input filtering with smoothing gain
Copter: integrate smoothing gain into flight modes
Copter: ch6 tuning of RC_FEEL_RP
Copter: remove unused reset_land_detector
Copter: remove CLI set

Frees about 1k of flash
RC_Channel: added percent_input() function

useful for plane flaps
Plane: use percent_input() for flaps
Plane: removed some unused functions
RC_Channel: added support for separate wheel steering channels on planes
Plane: added support for a separate steering channel

good for ground steering on larger aircraft
Rover: support k_steering channel
Copter: remove CLI tests for gps, logging, radio

Required to shrink the firmware down so that it can fit on the APM2
boards
Git: ignore xml files produced by Plane autotest
Copter: move report_compass out of the CLI

This function is also used by compassmot.  Having it strictly part of
the CLI causes a compile error when the CLI is disabled