change sm:delete-group() to sm:remove-group() in tests
stop using deprecated xmldb:group-exists()
stop using deprecated function xmldb:remove-user-from-group()
stop using deprecated function xmldb:add-user-to-group()
stop using deprecated function xmldb:exists-user
stop using deprecated function xmldb:create-user()
stop using deprecated function xmldb:change-user()
stop using deprecated function xmldb:delete-user()
stop using deprecated function xmldb:get-user-groups()
use non-deprecated versions of the group membership/managership list functions, create-group(); add a mostly-unused description field to the group schema
addition and removal of group managers, closes #60