OpenSystemsDevelopment / qpdf

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.

Fix typos in cli.rst

This is used to generate a schema for the job json, which can't
contain `)"` because it breaks the R"(...)" syntax in C++. While C++
accepts R"anything(...)anything" to avoid this, as of this writing,
MSVC 2019 doesn't understand that. For now, just avoid it by removing
parentheses from the end of short help.

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.

The agogo theme doesn't do very well on narrow screens. The code
blocks were used for shell commands but were using Python syntax
highlighting.