docs: Add note about weird VLC behaviour on some versions.
cli: Expand ~ in default player paths.

Resolves #483.
plugins.ustreamtv: Fix channels using RTMP streams.
Update CHANGELOG.rst.
Update AUTHORS.
stream.hds: Handle relative URLs in manifests using href media.
plugins.afreecatv: Update for service changes.

Resolves #488.
Add plugin for NHK World (nhkworld).
Update CHANGELOG.rst.
stream.flvconcat: Ignore non-onMetadata script data tags.

Resolves #490.