local: Return multiple tracks from lookup()
Fixed flake8: I201 Missing newline between sections or imports
Change JsonLibrary.lookup to return a list
audio: Deprecate emit_end_of_stream
models: Hide empty lists from repr()
models: Fix equality for fields set to the default

Fixes #837
models: Make all fields default to None or empty collection
Merge pull request #861 from jodal/fix/837-model-eq

Cleanup model repr() and fix equality of models with fields set to default values
Merge pull request #855 from jodal/feature/emit-none-to-emit-eos

audio: Deprecate emit_end_of_stream
core: Remove clear_current_track argument from stop()
Merge pull request #840 from tkem/feature/local-library-lookup-multiple

local: Return multiple tracks from lookup()
docs: Update changelog with PR#840
Added a playback history object to the core.
TrackHistory stores Ref instances. Timestamp as epoch in milliseconds also stored.
Switched track name and artist order in history object.
Use assertIn instead of assertTrue to test membership.
history: Rename class to HistoryController

For consistency with other core controllers.
playback: Move comment so its next to the line it applies to
history: Use time.time() to get time since epoch
history: Import entire modules

For concistency with other code.