SoundSoftware Code Site

We need to be extra sure that

https://code.soundsoftware.ac.uk/projects/soundsoftware-site/repository/entry/extra/svn/reposman-soundsoftware.rb

won't ever assign to a project a repository that belongs to another one. For example: can a subproject have the same name as a top-level project? If a repository exists at all when this script runs, it shouldn't ever assign it to any project other than the one it's already assigned to.

Review this. Also, document the procedure as we now have it at https://code.soundsoftware.ac.uk/projects/soundsoftware-site/wiki/AuthenticatingHg (refer to issue #9).