code: public BasicSebConfiguration addSystemPropertiesAfter(String afterKey) {
  		return (BasicSebConfiguration) addPropertiesAfter(afterKey, SYSTEM_PROPERTIES_KEY, System.getProperties());
  	}
docs: Adds {@link System#getProperties()} after specific key in actual
  properties list.
  
  @param afterKey
  The after properties key
  @return Same instance