Give a GroupFeature element a location and a direction

[GitHubDaveSmith]

An approach that has been suggested for doing this in QIF would be to add a line and a point (or perhaps just a point, which has a location and a direction) to represent these values. The question is, how would a third party know that this point holds the above properties of the group? A specific mechanism for allowing this would remove any ambiguity for a consumer of the instance file.