Revert "Merged quality branch"

It's not a good approach to have p.a.imaging depend on p.namedfile.

This reverts commit 031bd2a4b3cccf404f7bd9aefb7f0c26cb5d013b, reversing
changes made to cc60b0f94008b6e34317fc45b720a2f83fc20706.

Conflicts:
	plone/namedfile/scaling.py