Ogm 547 unique constraint on properties

https://hibernate.atlassian.net/browse/OGM-547
The message will look something like:
```
OGM001404: Neo4j does not support constraints spanning multiple columns: org.hibernate.mapping.UniqueKey(UniqueConstraintTest$EntityWithConstraints[org.hibernate.mapping.Column(n(tableConstraint), org.hibernate.mapping.Column(naturalId)]) as UK_gvv44a4cq2qq3ywhofk552jrn
```

I would not say it is the most natural way to say it but it gives all the information needed.