Misc changes for multi videobridge support and other things
This is quite a large MR with some refactoring and new features. Among other things, it fixes these two issues:
It also makes it possible to (somewhat) easily deploy a setup where there are multiple videobridge running on different hosts than the jicofo/prosody. That said, I have not tested if the single-node setup still works.
None of the changes I made are documented (especially the new parameters). Where necessary I added some explanation to the git commits, but those are somewhat terse because I was still in the process of setting things up and didn't know what I'd actually keep.
I'm mostly posting this in case it is useful for someone and because I saw that you have open issues. Feel free to cherrypick whatever parts you like. If time permits, I'll update the documentation and/or fix issues you find, but I can't promise anything.