Add a filter row to the table view in the browse tab

Add a row of line edits between the table header and the actual content
of the table in the browse tab. Show one input widget per table column
in this row.

Add a live search which hides any table rows which do not fit to the
current filter settings.

Why add this to the parital-data-fetch branch? Because this is an
attempt to get rid of the find dialog which is broken again and not even
worth fixing. Also there is not much to break in this branch at the
moment ;)