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