Manage event data stream from DB

[oubiwann]

We need to create a new server in the mush supervision tree that manages event data.

Blocks #39

Depends upon: #40, #41

Tasks:

• [x] Examine simple pubsub options for Erlang apps
  • [x] ~gen_event~ not fully applicable
  • [x] gen_server
  • [x] @rvirding's chat_demo <-- good stuff! This is basically "use gen_server" with lots of the thinking already done 😄
  • [x] ~https://github.com/uwiger/gproc~ too much
  • [x] ~https://github.com/cabol/erlbus~ too much and maybe not stable enough ...
  • [x] ~https://github.com/cabol/west~ too much
• [ ] Implement a server based upon @rvirding's chat_demo (linked above)
  • [ ] just support running within a single node / release
  • [ ] provide an API for:
    • [ ] processes to subscribe to events
    • [ ] processes to receive events
    • [ ] processes to unsubscribe from events
  • [ ] integrate within existing supervision tree for hxgm30.mush or hxgm30.store
• [ ] Listen for DB changes
• [ ] Parse the results
• [ ] Perform actions based upon these (update game state? send messages to users? iow, utilize pubsub)