preserving pfix

[krober10nd]

• If user passed pfix, previously CGAL finite vertex iterator could scramble the location of pfix.

• Now if the user passed pfix, the program calculates the location of these points in the mesh and finds their index each iteration.

• Need a test.

• MWE

 import numpy as np
 import SeismicMesh

 import meshio

 hmin = 0.05

 pfix = np.linspace((0.0, 0.0, 0.0), (1.0, 0.0, 1.0), int(np.sqrt(2) / hmin))

 cube = SeismicMesh.Cube((0.0, 1.0, 0.0, 1.0, 0.0, 1.0))

 points, cells = SeismicMesh.generate_mesh(domain=cube, edge_length=hmin, pfix=pfix)
 meshio.write_points_cells(
     "cube_wpfix.vtk",
     points,
     [("tetra", cells)],
     file_format="vtk",
 )

[krober10nd]

addresses #95