AC_PosControl: freeze feed forward and vector fixes
AC_AttControl: rate compensation for yaw
AC_PosControl: freeze feed forward for alt control in Auto
Copter: Remove acro acceleration slew todo

It has already been done :)
AC_AttControl: zero _accel_xyz_max stops feed forward

Also added place holder for turning off feed forward.
AC_AttControl: clean up stabilize
AC_AttControl: formatting fixes
AC_AttControl: add earth frame angle constraints

This should help recovery time if pilot switches out of ACRO (into
Stabilize, AltHold, etc) while inverted
AC_AttControl: remove resolved To-Do

This To-Do is resolved by heli flight modes calling the
relax_bf_rate_controller method
AC_AttControl: move freeze_ff to flags structure
AC_AttControl: RATE_FF_ENAB param to disable rate feed forward