This class is largely a pre-C++11 holdover. It is now possible to
simply use move construct/assignment directly.
In a few rare cases (eg, polyMesh::resetPrimitives) it has been
replaced by an autoPtr.
- simplify structure.
- protect against nullptr when resetting memory streams
- make UIListStream swappable
- add uiliststream as an example of using a plain std::istream
- more consistent naming:
* Versions that hold and manage their own memory:
IListStream, OListStream
* Versions that reference a fixed size external memory:
UIListStream, UOListStream
- use List storage instead of DynamicList within OListStream.
Avoids duplicate bookkeeping, more direct handling of resizing.
