OpenSystemsDevelopment / qpdf

I decided these were confusing and inconsistent with how JSON works.
They muddle the API rather than improving it.

This reverts commit dc059560e73e0b373a6e54e71b07e3af4b692cb4.

I changed my mind. There's no harm in leaving it deprecated for a
release cycle.

See ChangeLog for rationale for not deprecating it as originally
planned.

Remove the name/number tree object helper constructors that don't take
a QPDF&.

* Don't surprise people with deprecation warnings
* Provide detailed instructions and support for the transition

This is a massive rewrite of the help text and cli.rst section of the
manual. All command-line flags now have their own help and are
specifically index. qpdf --help is completely redone.