OGM-454 Creating "model.spi" package for Tuple, Association etc., key types and meta-data types
OGM-454 Moving grid dialect operation context types to "dialect.spi"
OGM-454 Moving SchemaDefiner contract to "datastore.spi"
OGM-454 Creating "dialect.queryable.spi" package
OGM-454 Moving AssociationStorageConverter back to "impl"