Blurred thumbnail preview + progress bar

Displays a blurred version of the thumbnail
while the actual image loads
Displays a progress bar showing the image load progress
Animates into focus once the actual image is loaded

Change-Id: I2b8bc4691c20ffb5b3f16da9a8b9d6fd1796d784
Mingle: https://wikimedia.mingle.thoughtworks.com/projects/multimedia/cards/146
Merge "Blurred thumbnail preview + progress bar"