[O] point out extra export options in manual

[Eric Abrahamsen]

Whilst trying to figure out how to shut off the postamble in HTML
export, I realized that there are far more export-related options
available than those listed in section 12.2 (Export options) of the
manual. I had never really looked at the Publishing section of the
manual (13.1.5), because I've never wanted to publish whole projects.

If the list of LaTeX/HTML export options in the Publishing section is
the canonical full list, it would be nice to mention in section 12.2
that the options selectable through the #+OPTIONS syntax is only a
subset of the full list, and provide a pointer to the Publishing
section.

I can bang together a documentation patch for this, if desirable,
otherwise please let me know if I've missed some crucial part of the
documentation that would have made this clear.

Thanks,
Eric

PS: I've seen people provide links to Info pages directly in their
emails (presumably only any good if the recipient is using an
emacs-based mail client), how do you do that? Will a regular Org format
link come through correctly? Well, why don't I try…
[[info:org:Configuration][Publishing Configuration]]