Create a new element of the type defined by the given element factory.
If name is %NULL, then the element will receive a guaranteed unique name,
consisting of the element factory name and a number.
If name is given, it will be given the name supplied.
Create a new element of the type defined by the given element factory. If name is %NULL, then the element will receive a guaranteed unique name, consisting of the element factory name and a number. If name is given, it will be given the name supplied.