Move zbar plugin to separate subpackage
    
    Plugin zbar require some heavy libs like
    ImageMagick-libs
    graphviz
    gtk2
    and others.
    
    Without it gstreamer1-plugins-bad-free-extras can be used on gtk2-less
    systems and requires more then ten megabytes less. For example I don't
    need all this for pulseeffects package.