[jdom-interest] insertChild in Element

[Jason Hunter]

> The best counter argument for this would be a list of methods in List that
> are inappropriate for Element.  The obvious one is add - once you get the
> underlying list, it would not be hard to add something like an output
> stream.  

Elliotte has proposed that PartialList sanity check object types.  It's
a technically reasonable proposal.  I'm adding it to TODO.txt.  (It's
another sanity check we may want to skip in certain circumstances.)

-jh-