Storage of playlistssongs

The Core should be able to download and store and save the songs/playlists created in either the metronome app or the device itself that way the user doesn't have to connect through bluetooth in order to access the playlists/songs each time.

We've already been thinking about adding the ability to control the setlist (switch songs) straight from the Core. Likely we would build this at the same time so you could store the currently loaded setlist on the Core... but there wouldnt be several setlists and the ability to browse the library. I'm curious why keeping the Core connected via Bluetooth the phone is an issue, as it kind of happens automatically so you don't really need to worry about it? Are we missing anything?

Changed the title from "Storage of playlists/songs" to "Storage of playlistssongs"