[packagekit] Filters and the UI

[Richard Hughes]

The yum backend now supports all the filter options, which means we get
four comboboxes on the pk-application search page. This isn't great from
a UI point of view, and I need some ideas on how to make this better. 

Currently we have:

   Development:   [Only development]

Which isn't good. 

We need a way to specify a on, off, or neither in the UI. Maybe we have
to rethink how we expose the filters to the user.

For me they are very useful when querying my system "find me all
not-installed devel files for libnotify", but I appreciate I might be in
the minority. Maybe we could put this in the menu bar or have some sort
of advanced search pane.

Ideas welcome,

Richard.