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Get rid of old outdated interface fallbacks.
Okay, but then you have to update https://github.com/plone/plone.app.folder/blob/master/src/plone/app/folder/dtml/addGopipIndex.dtml#L20 too.

Changing the name of a parameter is not backwards-compatible for code that is calling the function with keyword arguments. Probably not a problem in this case, but may be in other similar ones.