Making the postgres xmldb class more generic (Bug 1384473)

Changing the value from postgres7 to postgres as we are really only
supporting postgres 8.3+

Also updated the list of reserved keywords to contain all the reserved keywords
that exist in postgres 8.3.
And added new postgres 9.3 reserved words to end of list

Change-Id: Ia233b8f21bff9983cf6918691283886467a607e4
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>