faccessors need custorm equal_to_tol operation

[abuts]

This ticket is part of Re #1147 wich sorted main issues with equal_to_tol but left small independant things unfinished.

equal_to_tol operation is now defined on serializable and uses saveableFields to define what to compare.

faccessors have overloaded loadobj and saveobj which requere protected fields to be set, saved and loaded.
As saveableFields now returns protected properties, standard equal_to_tol can not access them so fails on objects comparison

faccessors need custom equal_to_tol operation.