OpenSystemsDevelopment / qpdf

Also, use methods to access objid and generation.

Remove redundant variables pages and next.

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.

Remove variables obsoleted by commit 4f24617.

* 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.