doc: Various typo/grammar fixes

Kevin Grittner <kgrittn@postgresql.org>

Commit: 64277753b48009d72a915b798f69634653868720
Author: Kevin Grittner <kgrittn@postgresql.org>
Date: 2014-08-30T16:05:30Z
Releases: 9.1.15
doc: Various typo/grammar fixes

Errors detected using Topy (https://github.com/intgr/topy), all
changes verified by hand and some manual tweaks added.

Marti Raudsepp

Individual changes backpatched, where applicable, as far as 9.0.

Files