PDO throws an exception when parameters are missing or mismatch, DC throws php warnings

PDO throws exceptions if you try to execute a query with a wrong parameter count or parameters named incorrect.

Doctrine\ORM\Query does nothing of such kind and only throws php warnings when wrong php array keys are accessed. Attached is a patch that corrects this behaviour to give a developer more feedback on this kind of errors.

Performance wise, on each _doExecute() 1 count check of params against set parameter mappings aswell as one additional check if each passed param really exists.