Use int values instead of strings for PostgreSQL booleans

## The Problem:
The current implementation for PostgreSQL uses strings 'true' and 'false' which are not working with PDO::ATTR_EMULATE_PREPARES.

## Solution:
Use ints like in the default platform implementation.

## Comments
* There are only 2 options working both with or without emulation: ints and booleans, but booleans are more complicated to implement.
* Tested only on my local php 5.4.9
* Fixed NamedParametersTest to use int columns instead of strings (does not work with PDO::ATTR_EMULATE_PREPARES when compare string column IN array of ints)
* Fixed DbalFunctionalTestCase sql parameters dumping (found while fixing NamedParametersTest)
* Added support for driver options configuration via phpunit config globals