I created a nicer blue arrow by default and
use standard icons on X11 where possible.
Note that we still need an alternative solution
for mac.

Reviewed-by:thorbjorn

Reviewed-by: Daniel Molkentin

Use QGridLayout to align header label and QStackedLayout for the pages
(in code, as it is not available in Designer).
Derive new class FilterLineEdit for filter widgets based on a modified
version of FancyLineEdit and use that in settings.
Rubber-stamped-by: con <qtc-committer@nokia.com>