remove unnecessary std::move from Operator ctors

Initially a pass-by-value then std::move pattern was used in the Operator constructors as it can be more efficient if an r-value is passed as an argument. Later this was changed to pass by const reference, since the performance impact is minimal and it is simpler code that doesn't allow the user to use the moved value. However the std::moves were left over, even though they now do nothing. This change removes them.