Add implementation of linspace
Something similar to the Python linspace would be nice for creating plots. See e.g. https://git.iws.uni-stuttgart.de/dumux-repositories/dumux/blob/94d352a457077cfc7ba86426d0fb43968a81c2d8/test/common/spline/test_cubicspline.cc for a simple implementation. One could add something like the Kahan summation algorithm, for better precision.