Bug 895526 - Part 0: refactor TestUpgradeRequired.
Bug 895526 - Part 1: add strings.
Bug 895526 - Part 2: informUpgradeRequiredResponse => disableAccount.
Bug 895526 - Part 3: EndOfLifeHandler.
Bug 895526 - Part 4: factor NotificationHelper out of CommandProcessor.
Bug 895526 - Part 5: add EOL handling hooks, and UI, to GlobalSession.