make both build fcts const

Sample/SampleBuilderEngine/ISampleBuilder.h

Sample/StandardSamples/BoxCompositionBuilder.h

Sample/StandardSamples/BoxesSquareLatticeBuilder.h

Sample/StandardSamples/CoreShellParticleBuilder.h

Sample/StandardSamples/CustomMorphologyBuilder.h

Sample/StandardSamples/CylindersAndPrismsBuilder.h

Sample/StandardSamples/CylindersBuilder.h

Sample/StandardSamples/FeNiBilayerBuilder.h

Sample/StandardSamples/HomogeneousMultilayerBuilder.h

Sample/StandardSamples/LatticeBuilder.h

Sample/StandardSamples/LayersWithAbsorptionBuilder.cpp

Sample/StandardSamples/LayersWithAbsorptionBuilder.h

Sample/StandardSamples/LayersWithAbsorptionBySLDBuilder.h

Sample/StandardSamples/MagneticLayersBuilder.cpp

Sample/StandardSamples/MagneticLayersBuilder.h

Sample/StandardSamples/MagneticParticlesBuilder.h

Sample/StandardSamples/MesoCrystalBuilder.h

Sample/StandardSamples/MultiLayerWithRoughnessBuilder.h

Sample/StandardSamples/MultipleLayoutBuilder.h

Sample/StandardSamples/ParaCrystalBuilder.cpp