Plane : APM_Control : Removed inverted flight logic and cleaned up tuning parameter labels

The inverted flight logic was going to be difficult to test and was as likely to cause a crash as prevent one for models with limited roll rates or inverted flight capability. It is recommended that a function that levels the wings by setting a zero bank angle demand be incorporated if pitch angle goes outside set limits for a period of time.

Tuning parameter labels have been changed to provide consistency with previous PID useage