Runtime Hash Updater

This has been a bit of a re-write of some of the underlying systems. Functionality should all still be the same with the exception of one new command!

/setpackurl URL

This command allows you to dynamically update the URL of your resource pack while the server is still running. This is useful for people who use third party hosting for their packs which give randomly generated URL's or someone who wants version information in the ZIP file name.