removed the original global_group add/remove/change functions.
changes to make s_group behave like hidden groups; rewrote the functions for dynamic creation of s_groups.
switched off debugging
removed the use of function replace_no_group.
get_known returns both group and nodes names.
added group name info to some fields of the the multi record, which also affect functions that use these data; remove the node from no_group if it joins in a s_group.