fixes #398
(and possibly on other errors, not sure what else raises ValidationError)
Ensures that the QNodes haven't already been processed Fixes #185
All saves on exisiting items do set / unset operations only on changed fields. * Note lists and dicts generally do set operations for things like pop() del[key] As there is no easy map to unset and explicitly matches the new list / dict fixes #18
Refs #190
