eliminate_superfluous_helper_tracks()
rename sub
rec_status(): return REC when source is type loop
correctly route track when loop devices are specified as source or send id
(e.g. "source loop,Master_in", "send loop,Master_in")
accept syntax: add_effect_chain <ident> <successor>
Fix EffectChain add() method not to break general use
while keeping special functions to restore correct effect order
during uncache_track