Migration of old data to new PouchDB

[blackforestboi]

When we update the plugin in production, users shouldn't lose their old data.

This is why we need to implement a migration process that automatically runs as soon as the plugin is updated on the users machine.

This process takes every entry from the SQlite DB and imports it into the PouchDB.

This is a invisible process for the user.

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[blackforestboi]

also important:

1. making sure that the transfer happened
2. Writing it modular, so that we don't have to refactor it too much when integrating it into Gerben's code.