mock: add mock.Artist
capi: add missing sp_track_offline_status type
capi: add missing definitions for *browser_add_ref
capi: image handling
capi: search subsystem
capi: playlist subsystem
capi: playlist containers
capi: user handling
capi: toplist handling
capi: inbox subsystem
capi: sp_build_id()
settings: add missing settings.
audio: fix raise for Python 3.
session: create spotify.Session for session management.
manager: port the session manager to capi.