Transport indicator

Some indication of transport capacity (a la C&C). Even specific units (small menu showing unit buildpics or something).

I can work on images for this if somebody wants to do the lua. I think it needs to be a pass-over thing, however, so you don’t see it continually. Either that, or have it cover up the icon draw for contents that we’re stuck with currently.

Transporting(by trepan) basically does this. All that needs to be done is replace the unit model with their icon.