Queue download if update asked per ID

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.

Will close #102 (closed) for now.

Also close some TODOs.