added one-to-one MapsId
added more one-to-one relationships
added primary key join
added one2one @MapsId
added one-to-one @IdClass
added one-to-one @EmbeddedId/@MapsId
fixed typo in purpose
added one-to-one bi-directional with primary key join
added one-to-one bi-directional 0..1 owning case
added one-to-one bi-directional inverse optional case
added one-to-one cascades
added JPA-QL todos