Documentation tweaks: ALTER USER, statement-based middleware

Two small patches attached, based on recent documentation comments
suggested on the web site.

First alters a few places that ALTER USER is suggested, mainly in the
context of changing per-user settings. If you're reading the HTML
documentation, and you click on ALTER USER, it takes you to a slim page
that tells you what you really wanted was ALTER ROLE. That's kind of
wasteful, and thus the idea to go directly there. Original doc
suggestion from Grzegorz Szpetkowski, I found a few more places to tweak
when assembling the patch.

Wording may be a bit weird in spots though, so I'm not sure this is
necessarily an improvement in all cases. Right now the description
around these says things like "debugging could be enabled for all
sessions under a given user name by setting this parameter with ALTER
USER SET". Making that ALTER ROLE instead saves that page redirect
shuffle for document readers, but is it as clear to people who may not
know user==role? Hard to say.

Second doc patch is more straightforward, and based on an observation by
James Bruce. The description of how read/write traffic can be scaled
with statement-based middleware was so terse that it was hard to
understand. His suggested rewording shows he didn't follow the idea it
was trying to communicate at all. The updated wording I'm providing is
more explicit and shouldn't be as confusing. While in there, I also
fixed the obsolete mention of Sequoia with the current Continuent
project name of Tungsten;
http://joomla.aws.continuent.com/community/lab-projects/sequoia
documents the name change.

--
Greg Smith 2ndQuadrant US greg(at)2ndQuadrant(dot)com Baltimore, MD
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