Flag Prospected Sites for Dvar

[prof_doom]

It would be nice if we had some visual indicator that we had already prospected a site as the Dvar.
It's not a big deal, but it would be good for the mid game, when you're still actively prospecting, but have covered a relatively wide area.

 

[RNGesus322]

Bumping, this would be a really useful feature, as somebody who's played Dvar.