move units to units::si

Documentation/Examples/geometry_example.cc

Documentation/Examples/helix_example.cc

Documentation/Examples/stack_example.cc

Framework/Cascade/Cascade.h

Framework/Geometry/BaseTrajectory.h

Framework/Geometry/CoordinateSystem.h

Framework/Geometry/Helix.h

Framework/Geometry/LineTrajectory.h

Framework/Geometry/Point.h

Framework/Geometry/QuantityVector.h

Framework/Geometry/Trajectory.h

Framework/Geometry/testGeometry.cc

Framework/Particles/ParticleProperties.h

Framework/Particles/pdxml_reader.py

Framework/Particles/testParticles.cc

Framework/Units/PhysicalConstants.h

Framework/Units/PhysicalUnits.h

Framework/Units/testUnits.cc

Stack/DummyStack/SuperStupidStack.h

Stack/SuperStupidStack/SuperStupidStack.h