Broken app.
Prepared files for new design (moved useful files, remove useless ones).
See #26.
Use updater.php for JSON file generation. Based on existing application
functions.
JS/CSS dependecie imported locally.
Moved files into sub directories. Fixed js / css urls.
Now record artist / album / song according to their indices.
Added `echo 'var data=' before json dumping.
Restored toggling (expand/collapse artist) function.
Wording: song -> track, div id changed (more semantic).
Restored album cover displaying.
prefix and artists splitted into two different variable instead of
being fields of a library variable.