Make MHS installable with "eups distrib"

MHS products are currently installed with ics_config 's pfsinstall – see EUPS PFS docs. This does allow installing tagged versions of groups of products.

DRP stacks are mostly installed with the existing eups distrib mechanism. The main advantage of this for our purposes is that all products and versions are all listed in a single text file (the "manifest") That file or its recipe can be put into a git repository.