_lp_color_map is now able to adjust to different scales

Given a second parameters, _lp_color_map is now able to display
different colors depending on a scale. The second parameter is the
lowest step on the scale and ten times it the highest.
the _lp_color_map will use a scale system

and not a step one
Simplify color map lookup

Thanks to François Schmidts (jaesisvm) for the previous work.