Better multiple alerts handling system

Just realized that static properties can be used in this context instead of the session. There's anything new but this method is quite easier (and neater) than the previous one we were using.
Better multiple alerts handling system #2
Merge branch 'master' of https://github.com/euantorano/MyAlerts into unstable

Conflicts:
	inc/plugins/MyAlerts/Alerts.class.php
	inc/plugins/myalerts.php