Idea for cue-sheet support.

[Bart Cerneels]

Hi team, here is a braindump after some chatting with Ralf on IRC.

- Detect cue-sheets in collectionscanner, report them as regular playlist files.
- SqlScanResultProcessor handles cue sheets different from other
playlists. Stores timecoded urls (partial playback) indatabase for
each entry.
- Handled as regular tracks from now on.
- Cue sheet users are happy?
- Profit!

There is a wish for cue sheet support in the collection. It will be
put on the release blocker list for 2.6. Ralf seems to want to do it
;)

https://bugs.kde.org/show_bug.cgi?id=187587