Refactoring VideoFile and LanguagePack out of main, into updates and i18n apps, respectively

We created 2 apps in the last couple of months, to try and separate out functionality of the main app.  While much of the new models and code were put into the new apps, relevant old models and code were left in main.  However, that code can be cleanly moved over to the new apps.

In order to cleanly address #853 and #855, now is the right time to move these models over.

This PR has no functional change.  The refactoring simply moved `VideoFile` and `LanguagePack` models out of the main app, and into the updates and i18n apps, respectively.  All code had to be moved across with the models.

The main concern for functionality is, by doing this model move, data is lost.  I added a call to `videoscan` upon updates, however, so this should mitigate any damage.  This is a good idea to do anyway.  Since the `LanguagePack` functionality hasn't previously been published, there's no concern of lost data there.