Added autoplay feature for automatic blinking of sources.  It is under a 
new menu called Display.
Added ImageLoadingDialogManager class.
Controller now uses ImageLoadingDialogManager.  Setting an item as done
that wasn't being waited on will just be ignored.
ImageLoadingDialogManager now stores the items it is waiting on as a set
so that if items are added multiple times they still only need to be set as
done once.
The application now tells the controller to try and display the current 
image as soon as the model starts its work.  This makes sure the image
loading dialog is displayed for the first image when using the new 
ImageLoadingDialogManager.
Merge pull request #140 from drusk/autoplay

*happy dance* Closes #119.