Bare use of `new` should be replaced with smart pointer

A few places such as in the depo sources, a bare `new` is used.  The heap object is correctly deleted in the destructor.  In this particular case, a `unique_ptr` would provide a more modern idiom if also identical behavior.

Note that components are held by `shared_ptr` and those that provide WCT flow graph nodes tend to live for the entire job, in practice.