Inspector: add minimal drag implementation to line graph markers. Make the
playback slider actually adjustable (but doesn't control playback).
Inspector: smokescreen marker now follows dragged playback marker on line graph.
Inspector: finish drag-n-drop event listener implementation for line graph markers.
Zoom in/out on ReplayInputLineGraph on vertical scroll and pan on horizontal scroll/shift+vertical scroll.
Change zoom interval to be centered on cursor's position within the line graph.
Update line graph marker positions when zoom is changed.