Remove all deprecated code

[Sintrastes]

After coming back to this project after awhile, and working on the companion project xen-fret, I want to take this project in a different direction.

For that reason, a lot of code will have to be deprecated, and some code will be split into different packages (e.x. playback utils, as this is no longer part of the "core" library, and we also want people to be able to use things like tidal with this lib.