Get the version compiled into the dll.

Kreuzung beat me over the head to do this (though I went a bit above and
beyond), but really, I wanted to do it anyway so I could display the
version in the GUI without having to hand-edit it in (highly prone to
error).
Ignore the generated cs files.
Display the full version info in the build window.

This should make bug reporting a little easier. I'll move the version
extraction code elsewhere and put the string in more windows later.
Use QF's git-version-gen.

Rolling my own was getting too close to copying existing code, so... This
gives me a better version number and also the dirty tag.
Cache the version string and display in all windows.