Support playing locally stored files

[Rudolf]

In my playlists I sometimes have added locally stored files, mp3's of music which cannot be found on spotify. These files that are located on my pc get synchronized with my android phone and ipad as soon as I choose to make the playlist off-line available on my phone and ipad.

Would it be possible to synch locally stored files on xbmc such that the add-on can play these files too? It is not required to make all the songs in the playlist off-line available, just the entries added from locally stored files. Spotify allows to synch with up to three devices.