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:

• Examine simple pubsub options for Erlang apps
  • gen_event not fully applicable
  • gen_server
  • @rvirding's chat_demo <-- good stuff! This is basically "use gen_server" with lots of the thinking already done 😄
  • https://github.com/uwiger/gproc too much
  • https://github.com/cabol/erlbus too much and maybe not stable enough ...
  • 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)