- need the units in namespace CLHEP

 - should enable explicitly for testing

 - including necessary build macro etc

- Be sure to only make a copy when the dictionary lock is held.
- Avoid making a string if not needed

- improved const correctness
- allow find to take an argument which is equivalent to the key

- Allows object to be a private member data
- Initialization of globally accessible Evaluators no longer
 requires a lock as static construction is guaranteed to be
 thread safe.

- Calls to evaluate are now stateless
- Taking the lock is now exception safe
- Less strings are copied

Geant4InputHandling: create G4PrimaryParticle with 4 vector that constrains also the mass, setting the mass after, affects the momentum