nested namespaces -> merge into one opening/closing line

GUI/Views/GUIHelpers.h

GUI/Views/RealSpaceWidgets/Particle3DContainer.h

GUI/ba3d/model/particles.cpp

GUI/ba3d/model/particles.h

GUI/utils/Helpers.h

Sample/Multilayer/MultiLayerUtils.h

Sample/Processed/ParticleRegions.h

Sample/Specular/SpecularStrategyBuilder.h

mvvm/model/mvvm/model/customvariants.h

mvvm/model/mvvm/model/variant_constants.h

mvvm/model/mvvm/utils/containerutils.h

mvvm/model/mvvm/utils/fileutils.h

mvvm/model/mvvm/utils/numericutils.h

mvvm/tests/libtestmachinery/toyitems.h

mvvm/view/mvvm/plotting/customplotutils.h

mvvm/viewmodel/mvvm/editors/editor_constants.h

mvvm/viewmodel/mvvm/editors/styleutils.h