Less smart backend

Removing a bunch of code, related to a superduper un-clever guesswork of how to start the backend.

The new stuff is a more distinct rule for when to start the backend embedded and when to start it as separate process.

The locking/pid-checking logic also doesn't require Redis, which of course is a big win. (Not sure where my head was, when I wrote it in the first place).

We're using Daemon::Control for all the heavy lifting.