SearchWidget, but it also contains a SearchLine.

SearchLine operates on a PlaylistSearch::Component in the same way that
SearchWidget operates on PlaylistSearch, so this adheres to that method
of splitting things up.

I can also reuse the SearchLine in my implementation of the more advanced
search widget which I comitted the first parts of last night.

svn path=/trunk/kdemultimedia/juk/; revision=240319