Update to MAPv4 public draft

This should be in line with the draft at: https://docs.google.com/document/d/1Jh8ULpw0jb8kyxV-Ygw9U0n-XqXkM6_V3jxfmnkebqo/edit#
Good catch, I'm trying to bring the property names in line with the attribute names used in the draft, with the idea that `ActiveTriples` could generate the context, at some point.