add test to verify null cast in boolean type
resolves #632 Fix null cast in boolean type in Postgres platform
refs #632 Remove is_null to be consistent with doctrine coding standard
Update PostgreSqlPlatform.php

Add new line after an IF statement to be consistent with the coding standard
Test to check null conversion with boolean type

Add functional test to check null conversion with boolean type. This test required NULL to be allowed in the table column.
refs #632 check boolean conversion with and without PDO type value

Add unit test to check boolean conversion with and without PDO boolean type
Fix boolean conversion with php 5.6
Revert change to fix php 5.6
Change assertEquals to assertSame