Rethink default permissions and allowed types

[tusmester]

As we added more types, default containers, user, groups and sample content, the default permissions and allowed child type settings became cluttered and too complicated.

Goal

Clean up default permissions and set default values that let new users work with the repo easily.

Allowed child types

• what can and cannot be put in a container
• inheritance: inherited types may be added automatically by adding the 'parent'
• handle on the ui as a separate allowed childtypes setting view (like permissions editor) not as a field on the edit view
• search for allowed childtypes (where is it allowed)
• separate lists for 'set in the ctd', allowed, denied types for a content