Core FF: rename -> IFormFactorPrism

Core/HardParticle/FormFactorBox.cpp

Core/HardParticle/FormFactorBox.h

Core/HardParticle/FormFactorPrism3.cpp

Core/HardParticle/FormFactorPrism3.h

Core/HardParticle/FormFactorPrism6.cpp

Core/HardParticle/FormFactorPrism6.h

Core/HardParticle/IFormFactorPrism.cpp

Core/HardParticle/IFormFactorPrism.h

auto/Wrap/doxygen_core.i

auto/Wrap/doxygen_fit.i

auto/Wrap/libBornAgainCore.py

auto/Wrap/libBornAgainCore_wrap.cpp