ARC-24: Multitrack Groovebox

- New installs open a demo song. Press Play to hear ARC-24 right away - Help is in the header (?). Quick Start, docs, and Feedback & Support without digging through Setup - Sampler Keys can keep the sample's length while you change the note (Length, on by default). Speed is still there if you want the classic tape sound - Optional metronome while recording a sample. Same click and tempo as the timeline, off until you turn it on - Import MP3, M4A, AAC, and FLAC as well as WAV and AIFF. Drop in files from Files without converting first - Import video as well as audio for sampler pads. The soundtrack becomes the sample - Live loop switching is cleaner. The next scene starts on the downbeat without the old loop ringing over it - Songs still downloading from iCloud now say so, instead of looking like an empty library - Chopping is easier to land on the downbeat, and the chop screen stays out of the way