Wiki refactored

I have decided to fork the wiki into two separate projects (for the moment). While this makes some things a little more difficult to do, I believe it will prevent a lot of headaches in the future. By giving Physics and Mathematics their own spaces, each one will be able to follow whatever development model suits it best.

Currently the Physics site is considered the core project, and user registration etc., happens there. User accounts created there will work on the Mathematics project as well, (and on this site, of course!). However, user privileges aren't shared between the two projects, which I think is a good idea. Of course this is all a lot of song and dance for a project with only one contributor ;)