Align n.add and n.madd

When adding a component with non-default attributes, n.add would not add the attribute while n.madd does, for example
n.add("Bus", "co2 atmosphere", location="EU", carrier="co2", unit="t_co2")
Does not add the attribute location, since it is not defined by default while
n.madd("Bus", ["co2 atmosphere"], location=["EU"], carrier="co2", unit="t_co2")
add the column location to the dataframe.