Implicitly migrate on import

[edsu]

In order not to require an extra init step, and for the user not to need to know when to update their database with a migrate, we can migrate the database every time a user does an import.

Implicitly migrating the database when importing will:

1. ensure that there is a complete database schema to import into
2. ensure that the schema is up to date with the latest installed version of warcdb

I'm not sure if we should create a separate ticket for detecting the case when the SQLite database is for a newer version of warcdb than is installed. Perhaps we can use the _sqlite_migrations table to determine this?

sqlite> select * from _sqlite_migrations;
migration_set  name          applied_at
-------------  ------------  --------------------------
warcdb         m001_initial  2023-10-20 10:24:35.114387

Closes #18