Create config for frontend or backend seperately
    
    1. init_web_config: create Config object for frontend, load
       configuration from `web_config.py`.
    2. init_backend_config: create Config for backend, load configuration
       from `backend_config.py`.
    
    And two new classes inherit from `Config` in config.py:
    
    1. WebConfig: representing the orchestrator frontend web configuration
    2. BackendConfig: representing the orchestrator backend workers
                      configuration
    
    Before calling init_{web,backend}_config, check sys.argv, if
    "fedmsg-hub*", "celery" or "build_module_locally" is present, it's
    running as backend.