Add optional address field in YAML file

[mattstratton]

It would be possibly useful to have the street address for the venue as a parameter; this will make the structured metadata work better. This is not pressing for now.

[mattstratton]

This actually is starting to seem more and more like a helpful field to me; not only for the structured metadata, but also to help generate content. We can easily have it display along with the venue name in some places, and even create automatic map links based upon it.