Developed a way to run the webapp on a remote or headless computer.

The webapp can now be started on a remote or headless computer, just specify --listen=address to make it listen on an address other than localhost. It'll print out the URL to open to access it.

This doesn't use HTTPS yet, because it'd need to generate a certificate, and even if it generated a self-signed SSL certificate, there'd be no easy way for the browser to verify it and avoid a MITM.

So --listen is a less secure but easier option; using ssh to forward the webapp's port to the remote computer is more secure.

(I do have an idea for a way to do this entirely securely, making the webapp set up the ssh port forwarding, which I have written down in webapp.. but it would be rather complicated to implement.)

Made the webapp rescan for transfers after it's been used to change a repository's group. Would have been easy, but I had to chase down a cache invalidation bug.