PlayerManger class and fixed the bug where it would continue to play
beyond the end of the list (by just repeating the last item).

Started switching the semantics of nextFile() to *not* include the currently
selected item but to defer to currentFile() in that case.

Added PlaylistItem::playlist() and replaced a bunch of casts in
PlaylistSplitter.

svn path=/trunk/kdemultimedia/juk/; revision=291933