gst-player: Minor tweaks.
docs: The example is now using PyGObject.
plugin: Add Plugin.broken decorator.
plugin.api: Add StreamMapper, a helper to map data to stream objects.
plugins.ilive: Update for service changes.

Resolves #563.
plugins.svtplay: Make use of the StreamMapper.
cli: Change the continuous HTTP mode to always fetch streams.
Update CHANGELOG.rst.
Update AUTHORS.