Removed FullFresnelMap in favor of (smart) pointer to ILayerSpecularInfo and removed clone() from the last

Remove layer index from ILayerSpecularInfo (making the class name actually wrong, but this will be fixed later on)

Refactorings for graded layer approach (2)

# Conflicts:
#	Core/Multilayer/Layer.cpp
#	Core/Multilayer/Layer.h
#	Core/Multilayer/MultiLayer.cpp
#	auto/Wrap/libBornAgainCore.py
#	auto/Wrap/libBornAgainCore_wrap.cpp

Making all parameters fittable.

Ensure that SimulationElements that are going to be added are always set (to zero if no calculation is done on a specific SimulationElement)