Update PostgreSQLDatabaseConfigurationHelper.php

In prepration for https://github.com/silverstripe/sapphire/pull/1319
Probably should accept this at the same time.

If someone knows of the relevant ALTER permissions in Postgres, feel free to implment.
Merge pull request #13 from ss23/patch-1

Update PostgreSQLDatabaseConfigurationHelper.php
API Upgraded module to use new database ORM