Update refactoring code, new file loader

[jmaleo]

This pull request introduces a new code architecture designed to facilitate the implementation of new features.

Additional updates include:

• A new file loader that enables users to load PLY files without a Mesh, using only vertex position and normal data. It also allows users to load meshes from other types of extensions, utilizing the read_triangle_mesh.h from libigl.
• A minor feature: during the computation of a dry run MLS, the program now displays the mean neighborhood size being considered.