OpenSystemsDevelopment / qpdf

Rather than adding yet another flag that is almost never useful on its
own, just have --remove-restrictions disable digital signatures. The
operations are still separate in the API.

Positional arguments are supported in a backward-compatible way, but
completion no longer guides users to it.

Add the command-line arguments. They don't do anything yet.

To reference another command line option description, `:qpdf:ref:` is needed instead of `:qpdf:option:` which is not resolved properly in the HTML documentation.

Avd xcsv brvtns.

Now --json-output just changes defaults. Allow output file with --json.

Add additional parameters that will be needed to call QPDF::writeJSON
in partial mode.

* Replace --create-from-json=file with --json-input, which causes the
  regular input to be treated as json.
* Eliminate --to-json
* In --json=2, bring back "objects" and eliminate "objectinfo". Stream
  data is never present.
* In --json-output=2, write "qpdf-v2" with "objects" and include
  stream data.

Also add stubs for top-level QPDF methods (createFromJSON,
updateFromJSON)

Testing json against schema requires an in-memory copy, so do it only
when requested by the test suite.