LP#1715503: make upgrade script abort if not running min support version

LP#1715503: make upgrade script abort if not running min support version

This patch causes the monolithic upgrade script to fail if the
database its connecting to isn't running at least Pg 9.4.

To test
-------
[1] Verify that 2.12.5-3.0-beta1-upgrade-db.sql will abort
    if used in a Pg database < 9.4; verify that it will work
    if the Pg version is at least 9.4

Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>
Signed-off-by: Mike Rylander <mrylander@gmail.com>