Creates a mesh structure with a rectangular geometry DESCRIPTION: This can function can be used to create a rectangular mesh (2D) USAGE: vmcmesh = createRectangularMesh(xsize, ysize, step) INPUT: xsize - rectangle width [mm] ysize - rectangle height [mm] dh - width and height of each triangle in the mesh OUTPUT: vmcmesh - mesh structure, contains the geometry of the system SEE ALSO: createCircularMesh, createGridMesh This function is provided with ValoMC