Implement parameter (placeholder) behavior.

[instabledesign]

For the moment there is no functional difference between Lexer::T_STRING and Lexer::T_INPUT_PARAMETER (except the query syntax)

For example
http://localhost/?query={model{{Disco}}}

( ! ) Fatal error: Uncaught Doctrine\ORM\Query\QueryException: SELECT p FROM Example\Orm\Entity\Product p WHERE p.model LIKE Disco in /var/www/html/Xpression/vendor/doctrine/orm/lib/Doctrine/ORM/Query/QueryException.php on line 52

( ! ) Doctrine\ORM\Query\QueryException: [Syntax Error] line 0, col 62: Error: Expected '.' or '(', got 'Disco' in /var/www/html/Xpression/vendor/doctrine/orm/lib/Doctrine/ORM/Query/QueryException.php on line 52

Todo: Implement correctly the Lexer::T_INPUT_PARAMETER behavior.