Download entire library

[Myp3a]

This PR adds an ability to download an entire user's music library.
How to use: use "library" instead of URL, like gamdl library. The script will fetch all tracks from the library and download them.
Small caveats:

• User's uploaded songs aren't downloaded
• Some songs has catalog_id, but they aren't in the catalog anymore, like 1660614296, hence the try ... except
• Parsing an entire library can be slow, around 4 min / 1000 songs

[BuethSam]

I see this was merged to dev in February but it's not in the current release. I would love to see this feature to be included in the future.