Make GraphDynamicsInterop utils usable by outside pacakges

[MasonProtter]

This PR does a couple of things:

1. Adds a field to Connector so that it can store a Set of connection_blox. The idea is that these are for holding new blox that only appear in connections, but aren't necessarily blox in and of themselves.
2. I then made it so that get_bloxs has a method get_bloxs(g, conns) which also fetches the bloxs that were in the conns fields (if any). The reason I had to do it this way is to accomodate the way that composite blox are formed, I couldn't rely on just adding the blox to the graph itself if the graph isn't accessed by Connector, and I also wanted to avoid adding the same itnermediate blox multiple times (sometimes synaptic blox want to re-use a synapse for efficiency purposes)
3. it reworks some of the GraphDynamics interop stuff to make it usable from other packages who also want to use them (and adds a very basic way to generate connection dispatches from a Connector object

[MasonProtter]

I no longer need 1 and 2 so I am removing them from this PR.