Cleanup and bbb removal

Reduced dependencies and declared them explicit.
Do not directly depend on ``Products.CMFPlone`` any more.
Pep8fied et al.
ATCT is now an extra require.
Skip Zope2 old style interfaces.
Stop Plone 3 support in 1.1 series (remove bbb+patches).
Get rid of old outdated interface fallbacks.
before in https://github.com/plone/plone.app.folder/blob/cleanup-and-bbb-removal/src/plone/app/folder/__init__.py#L14 there was already try except else block