WL-3190 Test role inheritance

We have redefined the way we think inheritance should block assigning
priveledges on a resource.

When setting group based access:
  1. It should not be inconsistent if roles are inherited.

When adding role based access:
  1. It should still be inconsistent if groups are inherited.
  2. It should not be inconsistent if roles are inherited,
     + **unless** the role in question is inherited.
WL-3190 Implement changes

The tests should now pass. Provokes changes to ListItem so that it behaves.
Merge pull request #27 from ox-it/WL-3190

WL-3190 Refine inheritance rules for content