[FEATURE] Option to adjust scaling and smoothing of elevation data

Is your feature request related to a problem? Please describe.

I was trying to generate a map from a city with some relatively steep hills. Looking at the result, the hills look way too shallow. With some tweaking of the Arnis source code I determined there are (at least) three things that contribute to this:

• The elevation values are scaled by 0.7, noticeably reducing the slope of steeper hills.
• The elevation data is smoothed with gaussian blur. The automatically picked sigma is a bit too large and ends up smoothing out steeper slopes.
• The elevation data has comparatively low resolution (e.g. a bowl-shaped basin with a diameter of ~75 m and an elevation difference of ~10 m between the highest and lowest point seems to be completely lost in the elevation data due to low resolution).

Describe the solution you'd like

I don't think there is much to be done about the resolution of the elevation data, but it would be nice if there were options to adjust the elevation scaling and smoothing. Alternatively, I think setting the elevation scaling to 1.0 and smoothing to the minimal amount required to get rid of visible noise in the elevation data would be good as well.