Add self parameter to Attack activity actor.
Add MinRange plumbing to attack activities.
Add MoveAdjacentTo overload for moving within a range.
Use MoveAdjacentTo for attack activities.

Fixes #2104. Fixes #2923. Fixes #4455.
Add self parameter to HeliFly.
Add range support to HeliFly.
WIP: Add Guard to aircraft.

TODO: Need the FlyAdjacentTo activities before this will work.