Add ability to set the notification duration and the persistence

Add ability to set the notification duration and the persistence.

We're using this components in our project and need some customization like this one:  we can choose if the notification is persistent or not, if not, for how long it should be shown?

Usage:

`$notification.info(title, content, duration, userData);`

**Duration** is optional (milliseconds): It allows you to set how long the notification is shown. Put `0` or `false` if you want a persistent notification. If not given it take the value in the setting (5000).