Start loading videos only when played
At the moment all videos start loading once the map appears. This causes lot of network traffic and decreases UI responsiveness, e.g.: https://zukunftswerk-stage.ci.dmx.systems/systems.dmx.linqa/#/workspace/58573
Videos should start loading only when the user actually presses the play button.
See dmx-projects/zukunftswerk#213
@jpn FYI