XWIKI-20907: Introduce the notion of required rights

* Add a new flag to XWikiDocument if required rights shall be enforced.
* Add the new flag to the filter stream and XAR APIs, increase the XAR
  version and adapt tests.
* Add the new flag to the REST API.
* Add the new flag to the edit form to support updating it.
* Add a DocumentRequiredRightsManager API to allow getting the required
  rights that are set on a document.
* Add a DocumentAuthorizationManager to check rights using required
  rights.
* Restrict edit right to users that have all required rights.
* Add a test for DocumentRequiredRightsReader.