Add functionality to import/export SQLite database as text files

[tmiw]

I've heard that there's a desire to be able to view the individual messages inside the paclink.db file. Right now, you need to download a SQLite database tool and run a Base64 decode on the message content to do so, which isn't trivial. My thought is to have some sort of import/export functionality that emulates the previous Paclink behavior by generating individual text files for each message and possibly also allow re-import as a backup mechanism.

Thoughts on this?