OpenSystemsDevelopment / qpdf

Avd xcsv brvtns.

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

* 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)

Flatten everything to make it easier to map command-line flags to
json. The old structure was an illusion anyway because there was no
mechanism to enforce that things were in the right place. This also
helps with future flexibility.

Use "file" consistently for specifying a file path. We use "filename"
when adding attachments for a completely different purpose.

The code was assuming everything was happening inside dictionaries.
Instead, make the dictionary key handler creatino explicit only when
iterating through dictionary keys.

Now still have to go through and implement the handlers.

Fix typos in cli.rst

All that's left now is input and output handling.