Thibault Saunier authored Apr 22, 2020 and GStreamer Marge Bot committed May 19, 2020

This was complexifying the implementation for very little gain.
Each source type should ideally have its own API.

In that patch we make it so we do not have to subclass anything
but instead use GESAsset to pass information about how the pipeline
should look like.

Part-of: <!175>