color mode fixed leads to unreadable maax value

[linnea]

a fixed color mode should always result in equidistant color maps
fixed points should set up the scale and max value

new linear color maps will now have 12 colors from the colorwheel (picked by hsv values) from blue (lowest) to red (highest);
new linear color maps are in fixed mode;
the stop point generally work from 0 to 1;

for absolute z values these assignment should be recreated when the user sets new min/max values

[Edit]
now there are equidistant and variable colormaps;
the stop point count is variable;

[ghorwin]

Milestone deleted