Add AI control radius that will display as in strategic mode

[garethyr]

This should be drawn with FrameMan primitives probably, and brains should generate it. This should be a new lua (r/w) and ini property for MOSRotatings - AIControlRadius (or something like that) that makes them generate this in a radius around them.

In data, all brains should have some value set for this.

This doesn't have to actually affect gameplay right now, since the specifics of how this'll work are still up for debate.