Merge branch 'develop' into feature/modify-spotify-playlists
config: Read configs in binary mode
config: Add encoding support to strings
config: Fix escapes in string handling
config: Extract encode and decode helpers from String
config: Make List use proper encode/decode helpers
Merge pull request #413 from adamcik/feature/binary-config-reading

Treat configs as binary data
config: Make tests discoverable and fix broken ones
Use helper function lookup_playlist_from_name() to resolve uniquified MPD
playlist names to mopidy playlists in all MPD playlist handling commands.
Also make playlist_uri_from_name map private.
Define a uri for all playlists used in the MPD stored_playlists tests.
config: Support lists in required validator
config: Strict config value init kwargs, also adds Secret
config: Update extensions with respect to config changes
ext: Update and fix extensiondev docs with respect to config
Extra MPD stored_playlist tests for duplicate names
docs: Note on debugging GStreamer
config: Specify we want bytes for default configs
Merge pull request #414 from adamcik/feature/config-value-kwargs

Make config value init kwargs strict.
docs: Mark command line options with :option:
docs: Add command line options