move search_item api to gtk-helpers - related #182

- it's needed for easier unit testing

Signed-off-by: Jiri Moskovcak <jmoskovc@redhat.com>
added search_item unit tests - closes #182

Signed-off-by: Jiri Moskovcak <jmoskovc@redhat.com>
Merge pull request #183 from abrt/gh182

added search_item unit tests - closes #182

Signed-off-by: Jiri Moskovcak <jmoskovc@redhat.com>