Supporting postgres simplifies deployments to environments such as kubernetes. Since sqlite doesn't work well on nfs shares it can be easier for databases to have a dedicated db set up that applications can connect to. Sqlite is easier for most deployments though, so this will default to that if the settings haven't been updated to support it.
This change does the following:
- Separate out SQLite from the DataLayer and adds a Postgres assembly for migrations as well
- Add a configuration setting for a postgres connection string that will be used if it is there, otherwise reverts to the original sqlite string
- Add a copydb command for the cli to bootstrap the postgres db
- A convenience script to update migrations for both dbs at the same time
- Add template tag support for multiple series
- Add series ID and contributor ID to template tags
- <first author> and <first narrator> are now name types with name formatter support
- Properly import contributor IDs into database
- Updated docs
