Make GEVER easier to support

[lukasgraf]

This issue collects topics and ideas to make our app better supportable.

These should eventually be split up into separate issues, to make them easier to estimate and have a better defined scope.

• Introduce a Supporter role.
  This role should have all the necessary permissions to perform support work, but not be able to access the ZMI or perform other actions that are dangerous.
  Roughly, this would probably be permissions similar to the Administrator role plus a few additional ones

• Introduce a support user.
  This user should be present on every deployment, and have the Supporter role assigned (plus Member and others as necessary).
  It's still an open question how this user should be created and managed. I could imagine that we might be able to leverage ftw.zopemaster for this purpose. Allow a particular user group to assume the predefined support user's security context, central authentication, create the user in source_users if it doesn't exist yet, and set it up with the appropriate roles.

• Create a way to view actual permissions in context for a particular user with the use of ZMI

• Create a way so safely delete objects (dossiers / documents) in agreement with customer.
  Maybe: Customer flags objects for deletion, support performs deletion, backup export of objects and a deletion protocol is created.

• Create a view (and add a link to it for the Supporter role) that lists the configuration details for a GEVER deployment (enabled features, settings, ...)