Require new comprehensive settings API behaviour test

• recursively acquire each node
  • requires function to get child nodes for a node, which can be implemented in terms of:
    • child_names / get_active_child_names() + getattr()
    • get_object_names() if isinstance(node, NamedObject) + __getitem__()
• check each node
  • requires function to specify each possible check
  • each check function enforces the required behaviour depending on the node's object type. We are only interested in types of returned values and exception behaviour
• we can test the active and inactive child behaviours
• we can test all attribute access, and get_state()
• how often we run the test will depend on how long it takes to run
• the test won't pass without the read-only changes