Mesh 3 : initial_points parameter for domain point initialization

[ange-clement]

Summary of Changes

Added a construct_initial_points parameter in domain creation.
With this parameter, we can save a custom functor in the domain that will be used wen initializing the C3t3 complex.
This functor must follow the Construct_initial_points concept.

Tasks:

• Add construct_initial_points parameter in create_labeled_image_mesh_domain
• Make an example
• Fix example mesh_hybrid_mesh_domain
• Add construct_initial_points parameter in all create_xx_domain of Label_mesh_domain_3
• Write Construct_initial_points_labeled_image into a header
• Make initialize_triangulation_from_labeled_image use Construct_initial_points_labeled_image
• Make it pass checks
• Document construct_initial_points parameter
• Document Construct_initial_points_labeled_image header
• Document example
• Document initialize_triangulation_from_labeled_image and initialize_triangulation_from_gray_image
• Make small feature page
• Maybe add a test ?

Release Management

• Affected package(s): Mesh_3
• Issue(s) solved (if any): fix Mesh_3 - document initialize_triangulation_from_labeled_image() #7469, discussion Mesh_3: should initialize_triangulation_from_labeled_image be a static function of image domains? #7537
• Feature/Small Feature (if any):
• Link to compiled documentation (obligatory for small feature) wrong link name to be changed
• License and copyright ownership:

[ange-clement]

Closed because not easy to implement. PR #7798 does this better.