Specify seraph config file location using a system property

We have a lot of JIRA installations in our company where some of them require different seraph configurations. In order to keep our installations as equal as possible it would be great if we could specify a system property which points to a installation specific configuration location path. Here's what i did in my own seraph fork:

	public static SecurityConfig getInstance() {
		if (instance == null) {
			String configLocation = System.getProperty("seraph.config.location",
							SecurityConfigImpl.DEFAULT_CONFIG_LOCATION);
			loadInstance(configLocation);
		}
		return instance;
	}