1) Allow an existing group to be one of the users in a group
2) The group characteristics (enunciation, timeout limits etc) of the new group being defined is to apply to the group being included.
For example:
      ? Group "ABC" exists and has no enunciation
      ? Group "XYZ" has group "ABC" as one of its users. Group "XYZ" is defined with enunciation.
      ? When a message is sent to group "XYZ", all users including group "ABC" is to receive a message with enunciaton.