Get the reinstaller working again

Finally had the time to get this back up and running! This reinstaller does NOT do anything with the GitHub repositories; it merely clones whatever is there. We should have instructions somewhere for how to delete and re-fork the repositories if someone wants a full reinstall from scratch.

Later on I'll do the promised OAuth linkage to allow people to do this from the Dreamhack server by running another command, but for now this will do.