DDF-580 Refactor popup notifications.
DDF-580 remove commented out unused variable
DDF-580 rework logic to display only one popup notification at a time
DDF-592 update documentation to require Java 7
DDF-597 Group notifications in dropdown menu under categories, add capability to dismiss all tasks or notifications in a category from the dropdown menu, notifications in dropdown menu display all fields
DDF-597 remove unused imports
DDF-597 add check for null
DDF-597: merged pull request #17 to allow notification to be dismissed in a group