User services under control of runit under turnstiled now default to the
`~/.local/state/service/` directory (and `~/.local/state/service-env/`
for the env vars). This mimics the system-wide runit setup, with service
templates kept in `/etc/sv` (in my case `~/.config/sv` for user
services) and active ones in `/var/service`
For now, putting the associated files simply within the books/ directory
as well is the simplest solution. It also removes some clutter from the
root directory. If we refactor later, this will be changed overall
anyway.
