Session should be the object holding the list of inputs parameters (e.g. synchrony) and the list of source callbacks. This also avoids mixing input when copying sources. Code could be improved but is operational.
Updated SourceCallback class to accept cloning, reversing, and visitors for saving./loading. New mechanism in Source to listen to key triggers for launching SourceCallbacks. Saving and loading in SessionVisitor and SessionCreator.
Creation of multiple DeviceSources is possible (also for multiple sessions and transitions) through centralized management of gst streams. Creation and deletion of a shared stream accross DeviceSources is handled.
Work in progress; Sources now have play/pause and associated play functions. Media player can play all playable sources, and adapts to control a media player when possible. Selection of play groups (to finalize)
