OpenSystemsDevelopment / qpdf

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

from "qpdf-v2" to "qpdf": [..., ...]

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

Remove any ambiguity around whether old or new value is being
returned.

When there is no context for writing output or error messages, use the
default logger.

This includes the output PDF, streams from --show-object and
attachments from --save-attachment. This also enables --verbose and
--progress to work with saving to stdout.

* 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.

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

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.