Model for 2 directions of a relationship

In issue #9 (closed) we discussed the obverse relationship and obverse relationship type, see that for the history of this discussion. I'm starting a new issue so we can continue to discuss while finalizing the minimum core Agent model and JSON-LD recommendations.

My concern: It really is only one relationship in many cases. Perhaps Friend is an exception? But in all the use cases we are dealing with in a value network, both have to agree for the relationship to exist, and the relationship is merely recorded. Activities could be recorded if wanted, such as Request to Join and Request Approved, or something like that. Or if it is a question of verification, some type of credentials could be added to the model to verify from both direction. But these things would relate to the relationship, not be a reverse direction relationship.

@ahdinosaur Thoughts?