Basic functionality for adding an additional message implemented. You can add a new message to a group, and remove a message from a group.
Still need to do:
Streamline the process for adding a new speaker, including properly handling multistart. This would involve automatically adding a message of each type with an "Add new speaker" protocol, or maybe just a more simple automatically incrementing the speaker id on a newly added speaker.
Test in game? This would be tricky. Maybe hack speaker id values to force the new message to trigger.
Allow adding addidional messages for a new speaker id.