Playback of ETL Through the Overlay UI

[planetchili]

Enable to overlay UI to setup and track virtual presenters based on ETL files.

• [ ] Harmonizing virtual playback session with realtime trace session in service (PID overlapping etc.)
• [ ] Allowing for multi-session operation, each playback session associated with its initiating client
• [ ] Actions for clients to cause service to load an ETL and prime it, as well as playback start actions
• [ ] IPM changes to accommodate tracking virtual pids
• [ ] IPM changes to provide UI for controlling ETL playback