Prism with arbitrary cross section

[myurkin]

A homogeneous right prism with arbitrary cross section (in xy-plane) given by a contour read from file (like -shape axisymmetric). Something like

-shape prism_arb <filename> <h>

(height is given in real units, not ratio as for many other shapes). The implementation can reuse many code from axisymmetric shape, but it is not completely trivial. In future, we may also use this shape (without height) to consider arbitrary 2D scattering problems.

We may also think about tilted prism, e.g. the cross-section is translated not along the z-axis but along along some other vector. Then the command line would look like

-shape prism_arb <filename> <x> <y> <z>

But this can be added later with backward compatibility.