doc: flux -h should list flux-config subcommand
doc: update flux(1) after rework
doc: correct flux-config usage output
doc: add flux-config(1)
doc: spellcheck man pages
doc: add internal help to flux cmd driver

flux help CMD displays manpage for flux-CMD.
Set MANPATH to [config man_path]:install-dir
so this works even when side-installed to a place not in the
system man search path, or in-tree (if configured).
doc: configure in-tree help

Set man_path in in-tree flux.conf to point to $abs_top_builddir/doc.

During the build in doc, ln -s cmd man1 to make man(1) happy.
(We could have git renamed cmd to man1, perhaps a more reasonable
naming convention, but I didn't think it was worth churning history)
doc: update flux(1) and flux.c for "flux help"
Merge pull request #23 from garlick/doc-updates

misc doc updates, add "flux help cmd"