Fixed "init" migration job.

done() has to be called, otherwise this migration is never marked as  'successful'.
Add a new "incrementalId" field.

This will be used for CMUpdater's new "incremental updates" feature.
Describe the update-path.
More work towards incremental updates support (still not ready yet).
Rename some methods in the ResultConverter to make clear that they belong to a Rom.
More class renaming to make sure that we're talking about Roms.
Implement error handling for incremental updates.
More work towards working incremental downloads.