Install doltgres as a service

Unlike with Dolt, we don't expect Doltgres users to have significant command line interactions with the primary binary. Therefore it makes sense to provide installers for Doltgres that more closely resemble other traditional databases:

1. Install to a standardized program executable location
2. Configure a service daemon to run in the background including after restart
3. Put configuration info in a platform-standardized location

We should also consider providing this functionality for Dolt, as an additional installation script bundled with release.