Fix Hydra Mac install target prereq version numbers

[Tom Goddard]

The Hydra Makefile target install_mac_app includes lots of prereq version numbers like the Python, numpy, qt, ... versions used to install the needed files. When prereq packages are updated this Makefile target breaks. Could have a foreign.make that holds all the version numbers, but Greg Couch was not enthusiastic about that and would prefer the version numbers just appear in the individual prereq makefiles.

Possibly the install_name_tool library paths can be updated in the prereq package Makefiles.

Needs some more thought about how Chimera distributions will know which prereq packages to include.

[Tom Goddard]

Hydra retired.