Object loader and rendering

[aromanro]

There is some benefit of having the vertices indexed. As it is now, it duplicates the vertices, adding unnecessary overhead (and it's more than simply a vertex, it's also the normal, the texture coordinates, whatever). OpenGL can deal with indexed stuff.

It ended it as it is now because I ported it from the ray tracing project, where it made sense to avoid the indexing complexity at the time when I implemented it.

As it's only a toy project, I'm not sure I'll do the change, but maybe later the code could be reused in some other project so it might be worth changing it.