Provides implementations of the "simple" wrappers for the mutable Second Class Objects (SCO's) supported by DataNucleus, so that we can intercept calls that will mutate the object. Please refer to section 6.3 of the JDO spec. This simple form of the SCO wrapper has a delegate and intercepts any mutating methods, marking the field as dirty. There is no "backing store" or lazy loading like in the "backed" wrapper, but this will handle cascade delete triggering