Add 'artificial throttling' as an option in config

[chrisbenincasa]

dizquetv added artificial throttling in several backend services, seemingly because when they ran it would affect the video stream (perhaps when hardware transcoding is not enabled). For folks that are running the new version on beefier machines, or are using hardware transcodings, we shouldn't artificially throttle the backend. We can give them the option of turning this on.

[chrisbenincasa]

FWIW, the 'throttling' seems like it actually just calls to setImmediate - likely to let any outstanding I/O calls to flush, etc. If this is really an issue (perhaps it's more apparent for concurrent streams?) then we could consider off-loading CPU-intensive task (time slot scheduling) to Node worker_threads