SumModel behavior

SumModel behavior

Method behavior

Summing several models and calling the respective method has the following behavior

method\models:	normed	mixed	non-normed
pdf	sum pdf	Error	Error
value	sum value	sum value	sum value
func	sum func	sum func	sum func

Normalization range

Iff all submodels are normed and have the same normalization range, the normalization range is taken from them (given the model is normed). Otherwise, an error is raised if normed (WIP keyword) is not given a Space