IN PROGRESS - issue CORE-4126: Add system notification display area to
DE. 
https://pods.iplantcollaborative.org/jira/browse/CORE-4126

Created a WindowType for system messages.
Merge branch 'gxt3-sandbox' of https://github.com/iPlantCollaborativeOpenSource/ui-commons-module.git into gxt3-sandbox
Merge branch 'gxt3-sandbox' of https://github.com/iPlantCollaborativeOpenSource/ui-commons-module into gxt3-sandbox
Merge branch 'gxt3-sandbox' of https://github.com/iPlantCollaborativeOpenSource/ui-commons-module.git into gxt3-sandbox