Resolve ""Height limitations on multicolormarker"
This MR relaxes the height limitations for the multicolor-marker to a non-negative height.
This makes it possible to input lower heights for tracking something else than a human (e.g. for testing a camera).
If a low value for height (< 100cm) is input, an informational Pop-Up appears, informing the user that the unit used is cm, not m. This should prevent issues arising from this.
Closes #140 (closed)