Migrate More to New Random Service Interface

Migrate SimWatchers and Hector related simulation code
to use the new interface of the random number generator
service designed to work with the multithreaded Framework.

The SimWatchers are different than other simulation
code because the call stack goes through GEANT
functions and engines cannot be percolated. So
SimWatchers use the global CLHEP engine (which is
the same thing the current version of GEANT does).
This CLHEP global will be a thread_local as soon
as planned changes are made to CLHEP.

The Hector code is different because it has TRandom3
hard coded in its interface, although it turns out
that does not really affect the migration.