meta-sequencer: save arp OR grid patterns

[dndrks]

current behavior: the meta-sequencer only saves played or random grid patterns, but arps do not have any save/recall system. they can be keyed in, windowed, paused, played, even saved with a collection -- but there's no "bulk" save/recall, where many arp patterns can be chained together.

proposed behavior: since arps are just clocked patterns, they should be able to be saved like regular grid patterns.

[dndrks]

fixed with #11