Re: DOCS: Make the Server Application docs synopses more consistent

My previous v2 patch needed a rebase anyway, so I've taken this
opportunity also to restructure everything. Although it would be
easier to post a single patch, some of the changes are still
debatable. For this reason, now I've split the previous v2 patch into
multiple parts, hoping that it will help all the uncontroversial
changes to be easily committed up-front, so that we can focus any
debate on whatever remains.

Please find the v3 patches attached:
v3-0001 - Refer consistently to the --pgdata directory as 'datadir'
(most commands already do this, but not all).
v3-0002 - pg_walsummary. Fix typo. "with" should be "within"
v3-0003 - pg_walsummary. Change 'file' to 'filename' and add the
missing option description for it.
v3-0004 - pg_waldump. Some <option> tags are wrong; they should be <replaceable>
v3-0005 - [option] should be [option...] and make it always first,
like 95% of all commands already do.
v3-0006 - pg_controldata should have an "Options" section with
descriptions for -D and -V, and -? options.
v3-0007 - docguide. Added some new style guidelines for the reference
page synopsis

There are still several previously discussed (earlier in this thread)
changes that are not in this v3* patch set. They haven't been
forgotten; I'll revisit those later after the above (simpler) changes
are dealt with.

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Kind Regards,
Peter Smith.
Fujitsu Australia