Integrate with PhpGt/SqlBuilder

[g105b]

PHP.Gt/SqlBuilder is not a way of generating queries from code, instead it's a way of building a representation of SQL, therefore this issue is not the same as #84 .

To integrate SqlBuilder, do the same check for SQL files but for PHP files. If there is a PHP file of the correct name, load it and check the expected class name is available, then instantiate it and call its toString function.

[g105b]

When a .php file is present, the Query class type will be PhpQuery (usually SqlQuery). PhpQuery needs creating, and this class should represent the PHP class, load it and handle the toString calling.