bugfix: consider a dual fitness to be correctly initialized from a pair
BUGFIX: correct handling of initialization security in dual fitness

Remove the operator= overloads.
Represent badly initialized dual fitness by a "?" for the feasibility.
Add templates types as members of the dual fitness
Overload setup in the dual fitness assignment, to handle comparison overloading
Use the feasibility of the current individual for the feasability of the metric in dual fitness assignment
Use a dedicated setup in dual HV metric, with feasibility