Create geometry library

[adelezaini]

This PR implements classes in Euclidean geometry in order to create objects in 3D space.

This is a WIP and aims to implement the following classes:

• [x] struct Point: 3D point with specific methods;
• [x] struct Vec: 3D vector with specific methods;
• [x] struct Normal: 3D vector with specific methods referred to surfaces;
• [x] struct Transformation: represents transformations in 3D space.