Automated DW dev instances

[roadrunnertwice]

I had some fixes I wanted to attempt and it looked like the Dreamhack service might be sleeping or something, so I put together an automated way to bring up a Dreamwidth dev server.

It seems to be in decent working order now, so I'd love it if some other people could give it a try and suggest improvements!

One caveat: make sure the develop branch on your fork (or whatever branch you set it to check out) is recent enough that #2412 is merged.