ENH: support emplace methods and std::unique_ptr for PtrList-derivatives

- emplace methods
  Eg,
      m.internalCoeffs().emplace(patchi, fc.size(), Zero);
  vs.
      m.internalCoeffs().set(patchi, new Field<Type>(fc.size(), Zero));

- handle insert/append of refPtr wherever tmp was already supported

COMP: incorrect variable names in PtrListOpsTemplates.C