LP#1357364: Allow for sites that may have the intarray extension already installed.

Signed-off-by: Chris Sharp <csharp@georgialibraries.org>
Signed-off-by: Ben Shum <bshum@biblio.org>
LP#1357364: Explictly create the extension in the "public" schema.

Thanks to Thomas Berezansky for the suggestion!

Signed-off-by: Chris Sharp <csharp@georgialibraries.org>
Signed-off-by: Ben Shum <bshum@biblio.org>