Pull Metadata from Junodownload, Boomkat, Bleep.com, etc

Hi all -

Love Beets and finding it immensely useful for sorting my digital music collection. I am not a developer myself, but am interested in the subject and attempting to learn some Python so that I can eventually contribute to a project like Beets.

One feature that would be incredible if implemented would be the ability to pull metadata from dance music sites such as Junodownload/Juno.co.uk, Boomkat, Bleep.com.

While the available metadata sources are great for _most_ styles of music, there are a lot of more underground releases in the dance/experimental realm that are not available through MusicBrainz, etc and are readily available on sites specific to dance music such as Junodownload.

No files, tests, or entry points are named. Start by reviewing how Beets currently obtains metadata and the requirements for Junodownload, Boomkat, and Bleep.com; the scope is complete when these sources can reliably provide the requested dance and experimental release metadata.

Written by the indexing model from the issue text.