Use dashes instead of nothing for spaces

I'm a bit afraid that if we end up having a lot of scripts in this repository, we'll also end up with ugly script names like addedxuserandsetupedx-cloud-init becaue the norm up until now has been to remove spaces from folder and script names.

This MR changes jitsimeet to jitsi-meet, which is also more consistent with the -cloud-init already available in a bunch of files.