API Serializer and DeSerializer are now split

Serializer + DeSerializer are now 2 distinct classes with their own
Interface
FIX Default DeSerialiazer shifts payload data array

Payload data was stored in a 'className' array key. The DeSerializer now
takes care of removing this.
FIX QueryHandler Update now returns a fresh record

updateModel() now returns a DataObject freshly fetched from DB. Allows
to check DB write was done properly.