Each module is assigned its own unique ID which is accessible via its edm::ModuleDescription. The id is assigned in a thread safe manner.
Fixed a merge conflict from white space differences compared to pull request #272

Conflicts:
	FWCore/Framework/test/event_getrefbeforeput_t.cppunit.cc
	FWCore/Framework/test/generichandle_t.cppunit.cc
Merge pull request #269 from Dr15Jones/moduleDescriptionID

Unique module ID