Queue API

[aikar]

Provide an API that can take a queue, and provide a queue processor.

Sync option: parameters to configure # of elements of the queue to process per run, and how long to wait in between each process of the queue.

game units should use the game scheduler to advance to next run and rl time units should use async delays to control for that (but return to sync)

Async option should also provide optional concurrency level, and delays.