IN PROGRESS - issue CORE-4126: 
https://pods.iplantcollaborative.org/jira/browse/CORE-4126

Refactored the code, moving the new system message announcing code into
the org.iplant.de.client.sysmsgs package.
IN PROGRESS - issue CORE-4126: Add new system message announcement to
DE. 
https://pods.iplantcollaborative.org/jira/browse/CORE-4126

externalized announcement text.
Fixed a regression bug

The notification counter is cleared when all of the notifications are
deleted now.