fix(timeline): modvColor is not used when scene gets removed
fix(timeline): modvColor is not used when scene gets removed

When the property "modvColor" is set on a fixture in a scene that was added to the timeline, it now
can also be removed and will be ignored in the future. This makes it possible to change the color of
a fixture using another scene.

Fixes #95

NERDDISCO/VisionLord,NERDDISCO/VisionLord,NERDDISCO/VisionLord,NERDDISCO/VisionLord,NERDDISCO/VisionLord,NERDDISCO/VisionLord