[kde-edu]: Draw math functions: improving features (about KmPlot and KAlgebra)

[Matthias Meßmer]

Hello,

one of the most important feature of KmPlot is (was) the constraint
scaling of the axis for printing so that the tics' distance is an easy
multiple or part of 1 cm.[1] This is very helpful for (younger) pupils
measuring coordinates. distances, and gradients by hand.

There are a lot of function plotters to generate better curves, but none
i know with this feature. So please don't drop this.

Best regards

Matthias

[1] As i remember this was one of the main reason for the original
developper.