Added last-login-date and datetime factory
Added last-login-date and datetime factory

* AbstractUser has now lastLoginAt. Is a DateTime, updated with an eventListener
* Created DateTimeFactory as a service. Returns now() in create() method
* Injected DateTimeFactory in AbstractFactory and created now() method
* Changed all `new DateTime()` in all places, in favor of $this->now()
* Fixed some tests

elcodi/MetricBundle,elcodi/MetricBundle