Enable TLS by default and add UI for client/daemon auth

Turns on TLS by default and uses public keys to authenticate access.

- This PR still may require further testing and input on the user experience.
- FSNotify support has not been added to detect changes to authorized_keys
- Implementation of proposal from #7667

@bfirsh please review and comment on whether this is missing anything needed
It isn't via a Unix socket on boot2docker or host management, which is the "default" for a lot of users. It might be worth explaining that this is how it works by default on boot2docker (and I can amend the docs for host management ;).