Store emergency and announcement alerts seperately.

Before this release, only one type of alert would be displayed on BU WordPress sites. The plugin would operate on the principle that any alert coming in should override any previous alerts and display the newest alert. However, as we have Emergency type alerts and Important Announcement type alerts this singular focus presented the possibility of an Emergency type alert being wiped out by an Announcement ( and less critically vice-versa). This release stores alerts by types so that both can be displayed without interfering with the other.