code: public XML addGlobal(Class<?> aClass,Global global){
  		checksGlobalAbsence(aClass);
  		findXmlClass(aClass).global = Converter.toXmlGlobal(global);
  		return this;
  	}
docs: This method adds the global to an existing Class.
  @param aClass class to edit
  @param global global to add
  @return this instance of XML