clarify relation of ConfigQuery and query for default

[Ichthyostega]

This is planning and specification work.

We use configuration queries and we have a DefaultsManager, which resolves queries for default configured objects. Here default objects are kind of an existential quantisation, where actually these "somehow existing" solutions are tracked behind the scenes. Thus, both are related to querying and both seem to be related closely to each other.

Yet still the exact relation remained somehow fuzzy. As usual with recursive facilities, I hadn't any serious problems implementing it (and especially to ensure termination), but I don't understand what's going on here. Moreover, as DefaultsManager uses the query subsystem, and the latter is assumed to fall back on the DefaultsManager, working out the theory is apt to save us some unecessary ping-pong calls between both.