When promoe was minimized or on a different virtual desktop when it was quit,
the visible setting of playlist and equalizer was set to false.
So even when those two were visible before switching to a different desktop
they where set to closed when promoe was started the next time
Moved positions and sizes of close and shade buttons to Skin
changed buttons to use PixmapButton
moved buttons from PlaylistWindow to PlaylistWidget and PlaylistShade
removed now unused Button
fixed position of shadebutton (was off by 1)
fixed icon of shade button in shaded mode
