Merge branch 'switch_process' into 'master'

Framework/Cascade/Cascade.h

Framework/Cascade/testCascade.cc

Framework/ProcessSequence/InteractionProcess.h

Framework/ProcessSequence/ProcessSequence.h

Framework/ProcessSequence/testProcessSequence.cc

Processes/CMakeLists.txt

Processes/HadronicElasticModel/HadronicElasticModel.cc

Processes/HadronicElasticModel/HadronicElasticModel.h

Processes/Pythia/Interaction.cc

Processes/Pythia/Interaction.h

Processes/Pythia/testPythia.cc

Processes/Sibyll/Interaction.cc

Processes/Sibyll/Interaction.h

Processes/Sibyll/NuclearInteraction.cc

Processes/Sibyll/NuclearInteraction.h

Processes/Sibyll/testSibyll.cc

Processes/SwitchProcess/CMakeLists.txt

Processes/SwitchProcess/SwitchProcess.h

Processes/SwitchProcess/testSwitchProcess.cc

Processes/UrQMD/UrQMD.cc