Rover: allow throttle nudging in STEERING mode

this better matches what AUTO does
APM_Control: added rate and angle steering controllers
Rover: update for new AP_SteerController API
APM_Control: remove public AP_PitchController::get_coordination_rate_of|cat()
APM_Control: enable integrator in ACRO rate controller

this work better for unlocked mode
Plane: added ACRO_LOCKING parameter

this enables/disables the attitude locking in acro mode, allowing acro
to be a pure rate controller
Plane: added GROUND_STEER_ALT and GROUND_STEER_DPS

this uses the new AP_SteerController steering controller developed for
the rover code to allow for ground steering of planes
Plane: give manual steering when still

useful for servo testing
Plane: split out the channel stick mixing

makes code a bit clearer
Plane: if pilot gives aileron input then disable ground steering

otherwise it would be very tricky to do a low pass!
APM_Control: change minspeed on steering controller to 1.0
AP_HAL: added safety_switch_state() function in hal.util

will be used by copter to check safety switch is set
HAL_PX4: try to reopen UARTs if safety switch is disarmed

this allows attaching to the USB port after power on

Pair-Programmed-With: Randy Mackay <rmackay9@yahoo.com>
autotest: tweak plane parameters
APM_Control: disable integrator below minimum speed

this reduces the impact on initial takeoff
AP_HAL: removed separate Console class

the idea of a separate console class was never really used, and just
added confusion in a HAL port. It also consumes some much needed ram
and flash space on APM2
HAL_AVR: removed Console driver
AVR_SITL: removed Console driver
HAL_Empty: removed Console driver
HAL_FLYMAPLE: removed Console driver