AthConfigFlags.py: Add method to set flags from command line
First step towards a CLI for ComponentAccumulator based athena. Allow to set any configuration flag from the command line. To use it, call
ConfigFlags.fillFromArgs(sys.argv[1:])
just before ConfigFlags.lock() in the main method.
Then one can execute: python myNewConfigTest.py input.isMC=False
Caveat: Wenn passig strings, the quotes need to be escaped in order to avoid shell-interpretation of them.