v1.1.0b - Preloading images and server improvements

I guess I did decide to work on this a bit more.

Changelog:

• The images in the uploaded files are now preloaded, which means they immediately appear with the rest of an uploaded file in the UI.
• Uploads are now delayed by the server rather than rejected with a 503 when it's cleaning up
• The available disk space on the server is now checked on startup, and it can be configured to stop if there isn't enough
• Also added the npm packages to the credits

v1.0.0b

This might be the only release, we'll see. It's got all the basic features but the scaling could be improved, and a few other small things.