AthMonitorAlgorithm - add a flag to be set if Alg is running in an the express stream
This is a preliminary commit. A flag to signal the Algorithm is being run in the express stream has been added, but is not yet used.
Adding an attribute to AthMonitorAlgorithm, but not rebuilding the derived Algorithms (which occur in many packages) causes a run time failure.
Once the new version of the AthMonitorAlgorithm is built, adding the use of the attribute (and testing the new code) can be submitted in a future merge request.