Fixed undefined index notice when attempting to reconnect a MasterSlaveConnection after close has called

#714 - ignoring PDOExceptions on PDO#getAttribute(PDO::PGSQL_ATTR_DISABLE_PREPARES) as per https://bugs.php.net/bug.php?id=68351

#714 - Adding a test verifying that attribute `PDO::PGSQL_ATTR_DISABLE_PREPARES` is set when using pgsql on PHP 5.6+

Add unit test to check boolean conversion with and without PDO boolean type

Add functional test to check null conversion with boolean type. This test required NULL to be allowed in the table column.