DAR-1732 when getWikiNotifications does not find the data in memcache, put it there after querying the database
DAR-1732 adding WallNotifications::getData method comment
DAR-1732 wall notification fix: app should be in lowercase
DAR-1732 using lockAndSetData in WallNotifications::addNotificationLinkInternal
DAR-1732 using lockAndSetData in WallNotifications::remNotificationsForUniqueID
DAR-1732 fix: lockAndSetData callback should return a value
DAR-1732 using lockAndSetData in WallNotifications::markRead