Convert boolean values as expected by PostgreSQL when inserting/updating.

Boolean values are not converted into their proper PostgreSQL equivalents when
inserting/updating. This is proper behavior in the Zend implementation as
explained here: https://bugs.php.net/bug.php?id=44791 . However, with this
commit, if RespectTypes is set to true then boolean values will be converted
as expected by PostgreSQL. I've also added tests for this.