Resolve differences in implied transfers

The spec has some looseness in the implied transfer area. For example the examples for pickup and dropoff are transferring custody when there is a different provider and receiver; while the Carbon Farm Network software allows implied transfer of both custody and rights, which works well for them. I had forgotten what we had.

Note that implied transfers came about because we are trying to keep the flows simple and more intuitive, instead of having to string together flows, like a transfer custody (or just a transfer) then a pickup.

I've been trying to work through this, and it is pretty complex in terms of figuring out the cleanest, simplest, easiest to understand solution. My first attempt (represented in the first commit here) was to make the kind of implied transfer dependent on the action, based on what might usually make sense intuitively, like if Agent A is the provider on a pickup, and Agent B is the receiver, the examples assume that an implied transfer of custody occurred when Agent B picked up the resource from Agent A. But there are a number of possibilities. This solution has the advantage of not needing any new properties. But it makes the flows look non-sensical when sometimes you see provider-receiver imply transfer of custody and sometimes you see provider-receiver imply full transfer. I put this up as a MR in case I want to come back to the commit of Nov. 16. (It also includes some cleanup of examples from moving properties into VF.)

Next attempt will add a custodian field and see if that is actually more clear and allows more explicit choice when they need it.