refactor authentication system

[GVogeler]

(follow-up to #556 comment ) The authorisation system needs a major refactoring, which distinguishes clearly between:

• owner of a document
• (owner of a collection as rights can be inherited from this)
• allowed editor (e.g. individually by sharing or by moderation or via collection hierarchy by archivist ('community': https://github.com/icaruseu/mom-ca/wiki/User-roles and https://github.com/icaruseu/mom-ca/wiki/Authentication#community )
  • author of last modification

Currently MOM-CA tests for eXist-collection-structure, atom:author, and xrx:userid in '*.charter.share.xml'.

This should allow separating single documents from the eXist-collection structure.

[GVogeler]

I don't see any need to keep the access rights in a separate document to the charter document itself, so I would suggest to move the infomation from *.share.xml into the charter-xml and add a rights section describing indiviual rights there.