Add ability to specify metadata for individual connections

I'm proposing adding the ability to specify metadata for a connection when creating that connection. These could be simple name value pairs or something more complex. It would be nice to be able to filter on this metadata when querying connections. As an example, say we have a connection between entity A and entity B with verb V. I would like to say that there is some metadata M on this connection, and M.foo = "bar" and M.biz = "bat". When querying connections between A and B, I would then later like to specify that I only want to pull connections that have metadata such that metadata.foo = "bar".