Want feature for Diesel SQL conversions

It'd be nice to have a feature flag that brought in support for converting oxnet types into SQL types, so they can be used directly in a database. The most relevant traits are [`ToSql`](https://docs.rs/diesel/latest/diesel/serialize/trait.ToSql.html) and [`FromSql`](https://docs.rs/diesel/latest/diesel/deserialize/trait.FromSql.html). There might be other convenience features too.