Refactoring in MagneticParticlesBuilder, clean up in App's CMakeLists.txt

App/CMakeLists.txt

App/src/TestPerformance.cpp

Core/StandardSamples/MagneticParticlesBuilder.cpp

Core/StandardSamples/MagneticParticlesBuilder.h

Core/StandardSamples/SampleBuilderFactory.cpp

Core/StandardSamples/SimulationRegistry.cpp

Core/StandardSamples/StandardSimulations.cpp

Core/StandardSamples/StandardSimulations.h

Tests/FunctionalTests/TestPyCore/CMakeLists.txt