Goal of this issue is to change all notifications/alerts within Piwik to ensure they all use the new material design style. The old style is at least used in the "UI demo page" viewable at:
It will look better and consistent to only use the new style everywhere. Not sure where the old style notification is used in Piwik (so far only spotted it in the Morpheus demo)
Should be mostly done now, except maybe in the updater etc. which would be fine.