further cleanup of process-sequence code

corsika/detail/framework/process/ProcessSequence.inl

corsika/detail/framework/process/SwitchProcessSequence.inl

corsika/framework/process/BaseProcess.hpp

corsika/framework/process/BoundaryCrossingProcess.hpp

corsika/framework/process/ContinuousProcess.hpp

corsika/framework/process/DecayProcess.hpp

corsika/framework/process/InteractionProcess.hpp

corsika/framework/process/NullModel.hpp

corsika/framework/process/ProcessSequence.hpp

corsika/framework/process/ProcessTraits.hpp

corsika/framework/process/SecondariesProcess.hpp

corsika/framework/process/StackProcess.hpp

corsika/framework/process/SwitchProcessSequence.hpp

examples/hybrid_MC.cpp

examples/vertical_EAS.cpp

tests/framework/testProcessSequence.cpp