- use the term 'group' instead of 'family' - prefix 'PSI_' changed to 'PMODULES_' for several shell vars.
- PSI_RELEASES renamed to PSI_DEFINED_RELEASES - set PSI_DEFAULT_RELEASES instead of PSI_USED_RELEASES - PSI_USED_RELEASES renamed to USED_RELEASES (and saved in PMODULES_ENV)