Smart pointers for operator-terms
Operator the list of operator-terms for (zot, for, and sot) is stored as
addFOT... the argument is copied and a new
GenericOperatorTerm is allocated on the heap using the copy-constructor. This leads to a duplication of construction and the raw-pointer returned by
new GenericOperatorTerm is never deleted. Maybe it is better to use smart-pointers there, and to not copy always the operator-term, only in the case that it is a temporary.