Implements NSCalendar+Helpers Extension
Notifications: Reloads FRC when needed
Notifications: Prevents loosing highlighted cells
Merge branch 'release/4.4' into issue/2398-out-of-order-notifications

Conflicts:
	WordPress/Classes/ViewRelated/Notifications/Notifications.storyboard
Merge pull request #2401 from wordpress-mobile/issue/2398-out-of-order-notifications

Fixes Out of Order Notifications