Additions to sensory planes

[Wout Mertens <Wout.Mertens#rug,ac.be>]

hey!

What I forgot to say:

in the model, I assume that an object is sensitive to a single signal
strength unit at a certain distance. If this distance is 0 (or imaginary,
for hardhearing objects :), the squares become a point. These, of course,
just have to be entered in the two lists once.
Also, you don't want to have a lot of point-sized sensitivity areas,
because these will have to be checked regardless of wether the object can
only begin sensing from a certain strength on.
This can be remedied by redefining r as the distance from the source of a
certain signal strength F, and 
R: 0 if the minimum strength sensitivity, m, is higher than F
   the distance at which a signal F can be sensed if m==F
   something I haven't totally figured out yet (I'm hungry) if m < F
     for linear signal decay, this should be easy to figure out, for the
     rest, you'll have to use the inverse of the function. Something like
     that, anyway.

Wout.