Allow fluent to accept an Dto object when assembling

[Sherpard]

Right now, FluentAssembler takes care of creating a new instance of the target Dto.

There are cases that it may be handy to have some control over which object the assembling is taking place.

ATM. what comes into my mind is some kind of extended assembling.

As an example: Aggregates: Car Dto:s CarDto, LuxuryCar extends Car. Assemblers: Car -> CarDto, Car,LuxuryCar

On the implementation of LuxuryCar it would be great to be able to use method previously defined at Car->CarDto assembler