Artist similarity plugin

### Idea
I want to write a small plugin which collects "similar artists from artist"
The first source can be last.fm: http://www.last.fm/de/api/show/artist.getSimilar
But I really want to go in direction of acoustic brainz and t-SNE

In the end, the data I will collect are weighted relations between artists and I'm not sure if sqlite directly s the best for doing this. But maybe with graphlite it can be interessting to stay on sqlite
https://github.com/eugene-eeo/graphlite

But in the beginning to evaluate artist relation I will work with https://github.com/GraphAlchemist/GraphJSON
and
http://graphalchemist.github.io/Alchemy/#/examples

beets plugin -> lastfm -> export as GraphJSON file -> Import in Alchemy.js

The issue does not name a file, test, or existing plugin entry point. First clarify the intended initial scope between collecting Last.fm similar artists, exporting GraphJSON, and exploring AcousticBrainz or t-SNE; done should include a defined plugin workflow and agreed storage and export format.

Written by the indexing model from the issue text.