Statement interface change

remove debug output var_dump($firstSchema);

Added mysqli driver.

Portability column forced to lowercase

When using a PDOConnection and the Portability wrapper, the default value \PDO::CASE_NATURAL int(0) and PHP constant CASE_LOWER int(0) got mixed up.

Fixed a few cases of where MysqliStatement::execute() did not throw a exception if a error had a occured.