[phenixbb] auto-open MTZ scheme

Dear Phenixers, Prompted by Randy Read, Kevin and I have agreed that Coot should be able to auto-open MTZ files with columns labelled groupname.F_phi.F and groupname.F_phi.phi and groupname.DF_phi.DF, groupname.DF_phi.phi for difference maps for any value of groupname, of course. (Any weights should be applied to Fs before writing the file). We were wondering what the Phenix community/developers thought about that idea (there's not much point in adding this feature if you don't agree). Thanks, Paul.