Expaneded the lua API for Regions

I've added lua hooks for both pager functor classes. Hopefully, I haven't
missed any corner cases, because it took me a while to hunt everything
down. One issue is that the map's save directory needs to be set in the
Format class, but it'll do for now. I'll review this again when I've got
more than one map running at one time.

There should be enough here for a lua-driven map generator to be
implemented, even if it's a bit rough. I think I'll test this out in the
editor eventually, but getting the base branch's network map code going
comes first.

The current process is extremely convulted, so I need to document
everything that I've done so far, including C++ and lua functions.