Gif upgrade

This is a pretty big upgrade. It adds the ability to upload animated gifs, storing a still of the gif, and the original at an alternate location (<image_id>/animated/original.gif and <image_id>/animated/original.jpg).

This branch also adds "imgmin" capabilities (inspired by https://github.com/rflynn/imgmin/), which will allows the server to determine an optimal image quality for each image, which should allow.