database and migrator revisions, help output, data model changes

- database:
  - moved to jackc/pgx from database/sql
  - revised migrator and moved it into it's own package
  - separated ParseConfig into it's own function
- config:
  - database config is now a DSN or URL instead of a struct
  - SearchPaths are now available through a function
- improved help / usage output
- modified data model

models/migrations/migrations.go

@@ -4,5 +4,5 @@ import (
 	"embed"
 )
 
-//go:embed *.sql
+//go:embed *.psql
 var FS embed.FS