Plan: Loiter Radius field should not be used for multicopters

The Plan screen has a "Loiter Radius" field which is probably populated from a parameter if using Plane. Copter doesn't have this parameter though so we should hide this field and never use it (for multicopters).

This field should also NOT be used (for multicopters) when drawing the circle on the map for LOITER_TURNS commands. If the LOITER_TURNS command's radius is zero then the circle should not be displayed because the vehicle will do a panorama shot (e.g. a pirouette, e.g. circle in place).


Start in the Plan screen where the Loiter Radius field is populated and in the map logic that draws circles for LOITER_TURNS commands. For multicopters, the field and radius must not be used; when the command radius is zero, no circle should be displayed.

Written by the indexing model from the issue text.