[WIP] REPO: Select the update function version

The version of the update function is chosen depending on the URI that
is passed to the update method of the repo module:
- An ID URI: the ___worker_update_from_ids is selected, the user will be
  able to queue the different kara to download by calling again the
  update method with others ID URI
- Anything else: the ___worker_update is selected. It will download all
  the database from Kurisu, filtering if the passed URI is not URI_NULL.

The aim here is to offer a download process option which permit the user
of doing a simple dry-update and then selecting the different karas he
wants to download id per id.