Coalesce thread_local statics in RunManagerMTWorker into one struct, and change boost::shared_ptr to std:: in SimG4Core

Coalesce the many thread_local statics in RunManagerMTWorker into a single thread_local struct.

In addition, change all boost::shared_ptr's to std::shared_ptr in SimG4Core.

No changes in physics is expected. Tested in CMSSW_7_2_GEANT10_X_2014-08-03-1400 with 100 TTBar events (wf 1302.0 step1), SIM-step gives identical results (runEdmFileComparison.py) before and after this PR for both OscarProducer and OscarMTProducer with 1 thread.