Allow make-dist.sh to use an alternative repo.

Adds the -u switch, allowing use of another repository than
http://github.com/diaspora/diaspora.git. This is a dogfood patch.
Renames diaspora-ws->diaspora-wsd; this is indeed a daemon.
Moves all Fedora-related stuff in make-dist.sh to subcommand
'prepare'. The source tarballs are now usable on any OS