Improve viewing of coloured tracks

Hi!

Coloring recorded tracks is a great feature. But I find that when your speed is fairly stable the result is disappointing since nuances are not visible. This because the "max/min" colors relate to max and min speed.

As an example when I have paddled a good distance and have speeds when paddling normally between 6 and 8 km/h, but also 0 when pausing and 10 in bursts, it is hard to really differentiate the effectiveness one had during normal paddling.

What about having an option to set the minimum and maximum speeds to be used for coloring the track? Then in this example I could set it to 5 and 9 km/h and have more than 50% increase in resolution. Then the nuances during normal paddling (which are the most important) will be very visible.

Speeds below or above the limits could be colored for example black and white.