Provide an example of relationship properties

[divideby0]

Firstly, thanks for this great sample.

I know Neo4j allows you to assign properties not only to nodes but also to relationships. I'm wondering if it's possible to do this via the neo4j gorm plugin directly. If so, it would be nice to include this feature in the sample app. For example, the relationship between a speaker and a talk could specify whether the speaker is a primary or secondary speaker.