Register event listeners with Velocity directly

[Phoenix616]

Currently events are forwarded manually to the Bungee plugin manager by listening on the related events in Snap.

Listeners should (where direct event equivalents exists) be directly registered with Velocity.

This most likely requires #1 be implemented first and will probably not work out for all events.

[Phoenix616]

There might be a major roadblock with this: Velocity only has 5 PostOrders while BungeeCord uses byte values for its event priorities which provide a potential range of 256 possible ones.