add a StreamID to the Pre/PostSource signals, and rename them to Pre/PostSourceEvent

 - modify the EventSourceProxy to pass the StreamID to the Pre/PostSource signals
 - rename the signals to Pre/PostSourceEvent (to be consistent with Pre/PostModuleEvent, etc.)
 - adapt all services to the change in the signals
The test was not properly thread safe

The guard only guarantees that the enclosed code is called no more than ’N’ times. The code being called must itself be thread-safe. This fixes a spurious test failure due to the thread-safety issue.
Merge pull request #1614 from Dr15Jones/makeCallXNoWaitTestThreadSafe

Multithreading fixes -- The test was not properly thread safe
Merge pull request #1575 from fwyzard/add_StreamContext_to_Pre_PostSource

Multithreading fixes -- Add a StreamContext to the Pre/PostSource signals
Merge remote-tracking branch 'origin/CMSSW_7_0_X' into CMSSW_7_0_X