HeppyCore: local multithread fixes:
- get exception stack traces when running multithread,
- support non-pickleable configuration with multithread
  (needed for the AutoFillTreeProducer in Heppy)
HeppyCore: provide also information on the component in which the exception was thrown
Multiprocessing fixes from Heppy
Merge pull request #178 from gpetruc/CMGTools-from-CMSSW_7_2_3

Fixes to Heppy for local multiprocessing