Getting ready for multi-backend system, where each backend would have its own configuration.
All 3 config structs (clap args, config, and configbuilder) are now separated into 3 files - the main one, one for service (actix stuff), and one for PostgreSQL.
The files have been moved to `/pg` and `/srv`, but otherwise the logic should be mostly intact.
* remove all actions and other low-level magic code, making it more straightforward for the most common usage
* replace r2d2 with bb8 to make it all async
* use first significant version in cargo.toml - this makes it easier to maintain
This fixes#349
This does not force automatic use statement sorting,
but it sorts all them now, and we can manually keep them ordered until
the fmt features becomes stable.
