Polyhedron Demo: Add sampling plugin

[afabri]

Summary of Changes

Add a plugin that samples meshes and polygon soups

Todo

• Add dialog for the various parameters of the sampling function
• Check that the input is triangular.

Release Management

• Affected package(s): Polyhedron
• License and copyright ownership: unchanged

[sloriot]

Successfully tested in CGAL-6.0-Ic-124 (but there are still todos)

[lrineau]

@afabri Will you finish the pull-request, or do you plan to delegate the remaining TODOs to one of us?

Or let me know if you want this PR merged as it is.

[github-actions]

This pull-request was previously marked with the label Tested, but has been modified with new commits. That label has been removed.

[afabri]

@afabri Will you finish the pull-request, or do you plan to delegate the remaining TODOs to one of us?

Or let me know if you want this PR merged as it is.

The todos are done now,

[sloriot]

• 196>C:\CGAL_ROOT\CGAL-6.0-Ic-127\test\Polyhedron_Demo\Plugins\Operations_on_polyhedra\Point_set_from_sampling_plugin.cpp(117,42): warning C4267: 'initializing': conversion from 'size_t' to 'int', possible loss of data [C:\CGAL_ROOT\CGAL-6.0-Ic-127\cmake\platforms\MSVC-2019-Community-Release\test\Polyhedron_Demo\Plugins\Operations_on_polyhedra\point_set_from_sampling_plugin.vcxproj]

• C:\CGAL_ROOT\CGAL-6.0-Ic-127\test\Polyhedron_Demo\Plugins\Operations_on_polyhedra\Point_set_from_sampling_plugin.cpp(117,42): warning C4267: 'initializing': conversion from 'size_t' to 'int', possible loss of data [C:\CGAL_ROOT\CGAL-6.0-Ic-127\cmake\platforms\MSVC-2019-Community-Release\test\Polyhedron_Demo\Plugins\Operations_on_polyhedra\point_set_from_sampling_plugin.vcxproj]

• C:\CGAL_ROOT\CGAL-6.0-Ic-127\include\CGAL/Polygon_mesh_processing/distance.h(265,38): warning C4244: 'initializing': conversion from 'const T' to 'size_t', possible loss of data [C:\CGAL_ROOT\CGAL-6.0-Ic-127\cmake\platforms\MSVC-2019-Community-Release\test\Polygon_mesh_processing_Examples\sample_example.vcxproj]

[sloriot]

Successfully tested in CGAL-6.0-Ic-129