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.
Handle optional choices in addition to required choices. Refactor the
way help options are added to completion to make it work with optional
help choices.
