Support for Podcast/Episode attributes explicit, block, complete, newfeedurl

[tkem]

• Explicit and blocked podcasts and episodes should be optionally filtered in the library (new config values). The iTunes extension can reuse the explicit setting from the Mopidy-Podcast configuration.
• Complete podcasts should be excluded from refreshing in the feeds directory.
• The newfeedurl property should be used in the feeds directory to updates podcast locations; a change of location should be logged, so the configuration can be updated to the new URI.

[tkem]

Still relevant for v2.0?

[tkem]

newfeedurl could generate a warning message, so people could upgrade their OPML files/playlists. This could be done in the RssFeed constructor.

[tkem]

explicit would probably have to be handled in the PlaybackProvider, too, for episode URIs coming from other extensions/playlists/clients.