Merge remote-tracking branch 'origin/master' into cleanup_process_interface

#.gitlab-ci.yml#

CMakeLists.txt

Documentation/Examples/cascade_example.cc

Documentation/Examples/staticsequence_example.cc

Environment/HomogeneousMedium.h

Framework/Cascade/Cascade.h

Framework/Cascade/testCascade.cc

Framework/Geometry/QuantityVector.h

Framework/Geometry/Trajectory.h

Framework/Particles/ParticleProperties.cc

Framework/Particles/ParticleProperties.h

Framework/Particles/pdxml_reader.py

Framework/Particles/testParticles.cc

Framework/ProcessSequence/BaseProcess.h

Framework/ProcessSequence/ContinuousProcess.h

Framework/ProcessSequence/ProcessReturn.h

Framework/ProcessSequence/ProcessSequence.h

Framework/ProcessSequence/testProcessSequence.cc

Framework/StackInterface/ParticleBase.h

Framework/StackInterface/StackIterator.h