Move logging/settings code to a separate process

[hannahwhy]

The ArchiveBot logging and job settings code has caused jobs to stall and prematurely abort a few times now. It should be moved out of the main wpull process and into a separate process.

This will help improve stability by clarifying the range of possible responses from a log write or settings read. (We either get what we want or an exception, and we can handle the exception by killing the helper process and optionally trying again.)

[hannahwhy]

Another reason to do this: the stuff that doesn't make sense at all. See #116.