height limitations on multicolormarker

When trying to set the height assumed of any given color, the minimum seems to be 50cm. I would suggest to change this hard limitation to just a warning, if values below 50 are entered. (Maybe someting like "the height value is in cm", just in case someone enters 1.6 while thinking it would be meters.)

In an older version, one could set the height below 50 by manual assigning it to a trajectory. This does not work anymore in the latest version.