album: Remove spotify.session_instance usage
track: Remove spotify.session_instance usage
artist: Remove spotify.session_instance usage
inbox: Remove spotify.session_instance usage
user: Remove spotify.session_instance usage
toplist: Remove spotify.session_instance usage
search: Remove spotify.session_instance usage
playlist: Remove spotify.session_instance usage

Except in callbacks.
session: Add get_link(uri)
link: Remove spotify.session_instance usage
image: Remove spotify.session_instance usage
utils: Remove spotify.session_instance usage
tests: Split playlist tests