Previously the rate controller disabled updating the integral below 20%
throttle. This is not ideal for several reasons:
- some racers already hover with 20% throttle.
- for acro it is important to always keep the integral enabled, it has a
  noticeable effect on flight performance.

 - px4_add_module now requires MAIN
 - px4_add_library doesn't automatically link

So that it can be customized better according to personal preferences.

The limitation of 16 chars did not allow to use a better param name.