Provide additional or alternative color scales (different from linear)

[MarcoMinghini]

At the moment, the color of each OSM node/way is derived from a linear interpolation of the colors of the rainbow scale from red to blue. The linear scale has the disadvantage that, for specific distributions of values (for any quality criterion), it might be very difficult to visually appreciate the difference of values. For example, if all the OSM nodes in a specific area have 1 or few revisions and there is only one node having 100 revisions, then all the nodes except this would have almost the same (red) color. This can be avoided by offering alternative (or additional) color scales, e.g. a logarithmic scale, or a scale based on quantiles of values, or a scale based on "equal counts".