Add documentation and code patches for maintenability

[pierre-dejoue]

• [x] Add documentation to README
• [x] List headers in cmake files
• [x] Code patches that should not impact functionality. The goal is readability and maintenability

Note: I found Thomas's image on Flipscan followin that link: https://blackflux.wordpress.com/2014/03/01/meshing-in-voxel-engines-part-2/

[jhasse]

Thanks!