Add ability to ignore files based on regex

This PR adds the ability to ignore specific files based upon one or more regular expressions matching their filename.  This is useful in preventing unwanted images from being considered for upload, especially when moving the images out of the way is cumbersome or impossible.  

One example is if you have had different sets of images (eg ``my-photo1.jpg`` and ``my-photo1.resized.jpg``), you can thus exclude anything with a regex of ``.resized``.  Another example is if you have specific photos you want to keep private or otherwise from not being uploaded, you could name them specifically in the list of expressions.