Various improvements

[frankrousseau]

Problem

• Playlist timeline is not properly located. Sometimes, it messes up with the video timeline.
• GLB animation can't be start/stop and be selected. ref: https://cgwire.canny.io/review/p/add-possibility-to-start-stop-gltf
• Playing pictures in the playlist, among other videos, is not seamless.

Solution

• Create a separate component for the playlist progress and move it below the button bar, above the entity list.
• Add start / stop button for animated GLB files.
• Add a progress bar and fix the duration to 48 frames for pictures.