Add the ability to reorder videos

[gerrgg]

Users should be able to reorder the videos using a npm package like: https://www.npmjs.com/package/sortablejs

We would need to update the Video's model to include a "order" property which would update via when reordered.

This would likely need to be specific to the user as otherwise it would get confusing quickly.

[gerrgg]

Seems less important now that we start with a random video/gif each time