Adds the command line option "--concurrent-events=N" which enables individual
control of the number of concurrent events as well as the number of threads in
an AthenaMT job.

If --concurrent-events OR --threads is used, the job is assumed to be MT.

If neither is set, then the job is not setup as AthenaMT.

If only one of --concurrent-events or --threads is used, the other takes the same
value (ie, same number of concurrent events as threads).

Both --concurrent-events and --threads can also be set simultaneously


Former-commit-id: f829830e

	* Tagging AthenaCommon-03-03-03
	* Adding an overlay task to the DetFlags

2015-06-04  Charles Leggett
	* tag AthenaCommon-03-03-02
	* add common concurrency opts (nProc, nThread) to ConcurrencyFlags
	  jobProps
	* added CONFIGURATION_ERROR to ExitCodes (0x09)

A       python/ConcurrencyFlags.py
M       python/ExitCodes.py
M       python/AtlasThreadedJob.py
M       python/AthOptionsParser.py
M       share/Execution.py
M       share/Preparation.py

2015-06-01  Charles Leggett
	* tag AthenaCommon-03-03-01
	* on behalf of John Chapman
...
(Long ChangeLog diff - truncated)