Return hash of published entry from create(), update() and delete() methods on session

[sandreae]

Currently each of these methods return the session instance itself (this) but for when you need the id of the created entry, returning the entry hash would be very useful. I can see the reason for returning this for the setter methods (setKeyPair(), setSchema()) as it's nice to chain these, but I can't really see the case where we need it for create, update and delete.