Rewrote methods to calculate next page url and to get items from it. `api-v2` is different from `api` since the initial playlist page contains (usually) the full info of the first 3 streams and only the id of the other. Then the single tracks can be requested in batch using `/tracks?ids=id1,id2,...`.
- Handle special cases for languages where the number is not shown
- Rework the Downloader base implementation, allowing for more
advanced things to be done
- Separate the localization from the content country (just like
YouTube let's the user choose both).