add a new model for square wells

the present version of the bound states lab computes the square well in the assumption of a finite barrier material. for educational purposes it would be quite nice if one could compare the numerical solution directly against the trivial analytical solution.

So can you please introduce a “Square Well – Infinite potential walls” model. THe parameter to replace the well width with would be “Maximum energy”

This way one can nicely generate a direct comparison to the numerical result.

This can be extremely easily done in matlab, but also in octave, or even in the fortran code directly.