* Move from using extending views to extending groups. Makes more sense - the group is the method of channel broadcast and usually you want to handle each message once per group.
* Improvements to the Debug page, plus the otree-redwood-debug component that can replay session events into the otree-events component for easier debugging without bringing up a new session each time.
* Includes a mechanism for generating custom output tables from the events for each group.
* The base Group can be configured to send period-start messages to signal all group members have loaded the page, connected to the websocket, and are ready to go. A period-end message provides precise control over the period length. This is more precise than the oTree timeout mechanism but less reliable - it won't survive server restart.