NOTIFPLT-38 Adds a read/unread state to notification portlet

Unlike the hide action, this might not be hidden after read
this is also permanent unlike hide which has an expiration
date.  This is meant to eventually persisted to a notification
store.
Merge pull request #6 from Jasig/markAsRead

NOTIFPLT-38 Adds a read/unread state to notification portlet