Ogm 521 natural one to one

https://hibernate.atlassian.net/browse/OGM-521

This patch will remove the redundant column created for *ToOne associations on nodes.
I add to add some metadata in the TupleContext to achieve this.
Yes, it might.
I don't  know exactly which tuple we are expecting given the EntityKeyMetada. Since we are not saving those columns it might make sense not to return them.
At the moment it is only used for the MassIndexing, and at some point the tuples are used to obtain the entities via TupleIndexer#entity(...). It seems to work but we need to check.