[Members] Re: Renaming git main branches.

While I don't think that this use of master (as opposed to master/slave) derives from the same usage, it's clear that some people do, and it's a small and easy change to make. I agree we should do it. The different repositories are under the purview of different teams, I think - the website is probably Board, the XEP repository is Editor, for instance. Happy to propose a policy from Board to push these all through though.