Unimplemented param GND_W_RMAX for ugv in v182 release

Attitude controller for ground rovers(src/modules/gnd_att_control/) had not implemented parameter “GND_W_RMAX”, which caused steering rate is out of control.
Parameter reference from here indicates the steering rate is being controlled but its params actually miscoded to be used by direct yaw control. That means the pid inputs _att_sp.yaw_body as setpoint, euler form of _att.q as current status,att.yawspeed as error derivative , but GND_WR* as pid params.
I suggested to add another group of pid params to realize yawspeed control.

The UGV implementation is an early proof of concept - we have a new developer starting on this in the next weeks - I will point him to this thread.