Updates: patterns, playlist and time signatures

• Several patterns per song: New, Clone, Rename, Delete
• Pattern length of 1, 2 or 4 bars
• Playlist of 32 bars, click or drag to paint patterns
• Pattern mode loops one pattern, Song mode plays the playlist
• Loop range in song mode (click a bar number to set it)
• Time signatures: 2/4, 3/4, 4/4, 5/4, 6/8, 7/8, 12/8