Kirigami: pageRow refactor ready for testing

[Marco Martin]

Hi all,
i think my rewrite of PageRow is almost done
here's a review request on phab: https://phabricator.kde.org/D1460
some test would be welcome, it should be pretty easy, just to switch
to the branch
mart/PageRow5.6
in the kirigami repo
from my tests on the gallery app it seems at least not to have
regressions (hopefully should work a bit better)
if from tests looks like it works better, I'll merge it shortly.

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Marco Martin