Use concrete number of grid regions

[pjaap]

Is there any reason why this had the minimal number 5 before?

[j-fu]

Well, what is happening n=1, 2,3 ? If it looks reasonable it would be ok to remove the minimum. But the result should be checked at least with gridplot with Makie, PyPlot and PlutoVista. Not sure if all these codes work e.g. with n=1.

[pjaap]

The GLMakie output is here: WIAS-PDELib/GridVisualize.jl#38
I'll check the other Plotters as well

[pjaap]

PlutoVista seems fine and shows now only 4 boundary segments. I am not familiar with it: Doesn't it show cell regions?

[pjaap]

But PyPlot crashes indeed. I will take a look there.

[pjaap]

PyPlot works with a few fixes: WIAS-PDELib/GridVisualize.jl#39

There was a wrong ncellregions instead of nbfaceregions and PyPlot.Colobar only works for n>1. I added a safety check to increase the number to 2 in case this is 1.

[j-fu]

Ok let us handle the problematic cases in the particular backends.