Un-remove IContentish from site root class

[jaroel]

On

Products.CMFPlone/Products/CMFPlone/Portal.py

Line 214 in 016459f

# Remove the IContentish interface so we don't listen to events that won't

I remove IContentish, because having it broke tests and setup code in places that I didn't feel like touching.

Nowadays we have some test failures because of the removal. See plone/plone.restapi#1674 (comment) for additional details, but suffice to say that conversation_view is expected to exist on the site root, but isn't because it's bound to IContentish.

[jaroel]

The removal of IContentish seems to also remove plone.app.relationfield.interfaces.IDexterityHasRelations (for PloneSite) . Which is weird to me because IDexterityHasRelations is set on the class plone.dexterity.context.Content, not as a subclass of IContentish.