Traveltorial/Misc fixes
 * Fixed log message in TraveltorialCreativeExporter.GetClickTrackerPublisherId
 * Make error for missing config setting in TraveltorialCreativeExporter.GetClickTrackerPublisherId an alert
 * Add WorkItemStatus.Failed to the expected statuses in Queue.DequeueProcessedWorkItems
   - Required changing WorkItemStatus to Flags enum

TODO: HandleProcessedWorkItems regression test for failed workitem handling
Merge branch 'master' of https://github.com/RareCrowds/OpenAdStack
Misc tweaks/fixes:
 * Improve ExportDynamicAllocationCampaignFxiture.ExportCampaign test stability by caching DateTime.UtcNow
 * Add Queue.DequeueProcessedWorkItems regression tests for un/expected work item statuses
 * Add defensive checks and improved logging to TimeSlottedRegistry.Move