hippo:document currently extends nt:unstructured rather than nt:base and includes mix:referenceable

By having such a free document definition if negates the use of node types. If furthermore creates issues like CMS7-283, but also is in the way of CMS7-545 because there are no longer protected properties (as all properties are allowed by nt:unstructured).

Not only is this an first step to getting CMS7-283. Current tests and development are building upon this misconception that hippo:document is nt:unstructured causing a huge amount of more work down the line.

I propose to make hippo:document more strict (by extending nt:base) and where needed to create an extended node type. The usage of this extended node type should provide the same functionality.
This issue is bound to spawn other issues, most of which can be pushed to a later milestone because we can have this extended node type as propesed, but executing the core issue we can expose the problems.