AC_AttControl: add RATE_RP_MAX, RATE_Y_MAX params

These replace the ANGLE_RATE_MAX parameter from the main code
AC_AttControl: tradheli add RATE_RP_MAX
Copter: add control_autotune.pde
Copter: integrate control_autotune
Copter: remove unused auto_tune.pde
Copter: comment fix for control_stabilize
Copter: APM_Config AUTOTUNE_ENABLED