Add DB serialization support

[cretz]

Added support for https://www.sqlite.org/c3ref/serialize.html and https://www.sqlite.org/c3ref/deserialize.html.

[FiloSottile]

I was about to send a PR to expose the same functions!

IMHO, bundling the schema name and the serialization does not make much sense, though. The schema name is a context-specific choice, not a property of the serialization. For example, one can serialize the main database, and then deserialize it later as snapshot.

[cretz]

IMHO, bundling the schema name and the serialization does not make much sense, though.

Agreed.