[Users] McLachlan BSSN

Please keep all discussion on the McLachlan BSSN code on this mailing list. This ensures that everybody knows about everything that is going on, and avoid duplicate work.

At the moment, we seem to have approximately three different versions of the BSSN code that seem to be incompatible: - the (official) trunk version - a version (potentially faster and more accurate) by Jim van Meter - a more flexible version (regarding gauge conditions) by Peter Diener

I would suggest that we discuss things on this list before we proceed.

John, Peter, could you describe your changes here?

-erik