Most of the code needs to be documented to make it easier for new users to develop games with the engine.

Utils::readAllLines gets the file using
Class.forName(Utils.class.getName()).getResourceAsStream(fileName)
which is equivalent to
Utils.class.getResourceAsStream(fileName),
and thus a user trying to read a file, e.g. when loading a mesh, will result in a null pointer exception if a file of the same name is not found within this repository; they cannot load their own files.

What is deferred rendering?
In deferred rendering, as the name implies, the rendering is deferred a little bit until all of the geometries have passed down the pipe; the final image is then produced by applying shading at the end.
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Why
Currently the engine uses forward rendering, which in some cases is not very performant compared to using deferred rendering.

The main performance factor is lights. If a scene contains multiple lights, it would be more efficient to use deferred rendering.

For now the project uses forward rendering as that is good enough for the current engine needs.