use baseline name to lookup

I thought that more code could move out of the MetacelloProjectRegistration towards the configurationProjectSpec or the baselineProjectSpec. This seems to work since MetacelloMCProjectSpec and subclasses can then decide how to handle themselves and not MetacelloProjectRegistration. I think that MetacelloProjectRegistration should have only one projectSpec variable.

A key change was lookupSpec: which found BaselineOfSeaside30 in my config when looking for ConfigurationOfSeaside30. This is nice because I'd rather use BaselineOfSeaside30. Generally, I think we should just enforce that precedence more.

Just some ideas, pick what you like.