work without a group type to pave the way for /group/<acronym>/ URLs,
make charter page more generic, enable it to handle descriptions and
walk over all personnel instead of picking out specific types
of roles, add a redirect view on /group/<acronym>/ to lead to either
documents/ or charter/, add simple group.features() class to be able
to condition on group features rather than specific group types,
adjust group pages menu accordingly
- Legacy-Id: 7758
