TODO

Playback without playlists
When clicking on the "previous song" button, the previous song should be played only if the current song hasn't passed 3 (5?) seconds. Otherwise, it should restart the current song. This is the common behavior in most music players.
Option to update the library (remove tracks that are not on the harddrive anymore)
Show YouTube video, not only the audio track (this should be toggleable via a button)
Show a different message when a song is missing on the physical drive (currently it says that the song is corrupt)
Handle songs from a removable drive in a playlist when the application is started, but the original path doesn't exists anymore
Possibility to repeat the playlist or the song

##Pro version

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