Ogm 547 unique constraint on properties

https://hibernate.atlassian.net/browse/OGM-547
Considering that in Neo4j constraints don't have a name at the moment, can't we say that there is not much difference between `RECREATE_QUIETLY` and `DROP_RECREATE_QUIETLY` and that the strategy I'm using is already implementing it? After all I'm creating the unique constraints ignoring the exceptions.

I would just update javadoc and documentation to make it clearer