Psr 3 logger

When `phalcon.register_psr3_classes` php.ini option is set, the following things are registered:
  * interfaces:
    * Psr\Log\LoggerAwareInterface
    * Psr\Log\LoggerInterface
  * classes:
    * Psr\Log\AbstractLogger
    * Psr\Log\InvalidArgumentException
    * Psr\Log\LogLevel
    * Psr\Log\NullLogger
  * traits (only for PHP 5.4+):
    * Psr\Log\LoggerAwareTrait
    * Psr\Log\LoggerTrait

Plus, if PHP is 5.3.9 or newer, Phalcon\Logger\Adapter implements Psr\Log\LoggerInterface. Also, Adapter and derived classes may throw Psr\Log\InvalidArgumentException instead of Phalcon\Logger\Exception when the input arguments are not valid.