Create centralised event broker between Web and Bancho

[cg0]

We want to be able to broadcast events between the two platforms, this will be using Redis pub/sub.

As part of this ticket we want to create an event that allows events within Bancho to be sent to Web and visa versa, these events should be then fired through the native event system but also allowing custom remote events to be listened to

The channel format will be event:ClassName and the body will be a JSON encoded form of relevant data, when it refers to database objects we should send the ID, so instead of User we would send user_id.

Each event on one platform should have a native event with the same name, this allowed each platform to listen to eachother's events allowing read-only processing without a companion plugin on each end

[cg0]

Web ticket: HirasawaProject/Hirasawa-Web#16

[cg0]

This ticket should also use environment variables for Redis credentials like #256