Update Caddyfile to Caddy v2
Fixes #2764 (closed)
The cache
directive has been removed, as it no longer seems to exist at all, module or not.
I've also removed the tls
directive, as the Caddy docs point out that messing with it is bad practice, and the Apache config doesn't seem to do it at all. (Though, if necessary, bringing it up to date as well should be trivial!)