Patch for "big features" section of release notes

All,

Attached is a patch re-arranging some of the features in the first part
of the release notes, as well as adding a few.  The additions are based
on (a) votes on what's a big feature for 9.0, and (b) a desire to match
the features listed elsewhere, such as the press kit.

--
-- Josh Berkus
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Josh Berkus                       PostgreSQL Experts Inc.
CEO                               database professionals
josh.berkus@pgexperts.com         www.pgexperts.com
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