Introduce the notion of document rights

In the context of XWIKI-20331 (see https://forum.xwiki.org/t/document-rights-management-improvement/12177 and https://design.xwiki.org/xwiki/bin/view/Proposal/Documentrightsmanagementimprovement), the intent is to define limited rights for a given document.
By default a document does not have script or programming rights, and they must be granted explicitly to be executable.
This improvements introduces:

• the storage at document level if this new restriction is activated
• the storage of the allowed required rights for a document
• the use of the required rights in the right validation code

Note that we found out several limitations to the implementation proposed in the current PR.