TODO

- Split up the Node properties AT_NREFS and CHILD_NODES so that links done
through primary-parent/child relationships are stored separately; a lot of code
can then be simplified (though some more complex); the system should be faster.

- Find some efficient way to maintain an index of surrogate ids for Nodes so
that using them isn't so expensive.  Currently, the code is optimized for those
people that don't use surrogate ids, and there is no overhead for index
maintenance.  After the change, index maintenance itself should have a very low
overhead or they may be more trouble than they're worth.  The use of them should
perhaps be controlled by a boolean Container property.

- Continue fleshing out the standard_routine enumerated type documentation.

- Rewrite the SYNOPSIS documentation to emphasize the simplest-to-use API.

- Add more deferred constraints to reduce erroneous models.

- Keep watch on the separately released "Rosetta" framework modules and ensure
we continue to meet their needs.

- Strive for complete code coverage in the tests.
