Configure PHPUnit and Behat to use separate schemas within PostgreSQL

It is possible to configure which database schema is used during installation for the main product, phpunit, and behat.
Separating PHPUnit and Behat into different schemas makes it easy interact with the data state for those things if you need to, without having to wade through thousands of tables because everything is in the one schema.

$CFG->dboptions['dbschema'] = 'public'; // Production.
$CFG->phpunit_dboptions['dbschema'] = 'phpunit'; // Unit testing.
$CFG->behat_dboptions['dbschema'] = 'behat'; // Acceptance testing.