pgsql: Further editorialization on the new documentation for statistics

Further editorialization on the new documentation for statistics views.

Get rid of the per-column documentation of underlying functions, which did
far more to clutter the view descriptions than it did to be helpful, and
was rather incomplete and typo-ridden anyway. Instead suggest that people
consult the definitions of the standard views to see the underlying
functions.

The older functions for obtaining individual facts about backends are now
somewhat obsoleted by pg_stat_get_activity, which means that they are not
documented by any standard view. So I put that information into a separate
table. (Maybe we should just deprecate them instead?)

In passing, fix a couple more documentation errors.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/5f2b0893871cce1ffb77ac7f13b3fba227e6f11f

Modified Files
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doc/src/sgml/monitoring.sgml | 423 ++++++++++++++++++------------------------
1 files changed, 185 insertions(+), 238 deletions(-)