tokens to have their own SSH keys

Since tokens are unguessable "users" without passwords, maybe tokens can optionally have SSH keys associated with them for added security. This would be optional.

It would also mean storing SSH keys, since we'd no longer be able to depend on the account owner's GitHub ... or rather, we could but it would start to get confusing and it's already a bit of a hack in the first place. So this also means building out our own SSH key store.