user controled height colouring

[chrfi]

it has become clear that trying to automatically remove high and low out liers from the colour generation is hard and complex. therefore a better method is to allow the user to control the height range the program uses when generating colours. anything above or below this height range is defaulted to the max or min value. this allows the user to remove outliers and also choose which height cross section they want to focus on (giving them higher colour resolution in the smaller height range)

preferable a pop out window, very small, with a couple of arrow buttons and text feild. the value is capped to the highest and lowest values and the max and min can be changed indipendantly (don't forget to prevent them making the min higher than the max)

[harg]

Done.