add 'parens', 'joiner' as argument that can be given to a nested group
or set based on group kind
used while formatting the group

add more tests from 'inclusive'

todo: clean up the 'key' kwarg from crosstest call
   label for group in error message, 'dest', usage?
   add title, description to nested groups
   cannot do exclusive(not actq , actwid) with existing groups
   can we control order in which groups are tested?