First exercise

A first small exercise to get started with OpenGL. The goal is a highly
optimized fractal planet renderer with fixed resolution which works with
a customizable set of LOD definitions. This exercise will touch the
following areas:

* OpenGL initialization and framebuffer configuration with GLFW
* Input handling with GLFW
* Multiple contexts with GLFW
* Multiple, thread-local contexts and their handling in OpenGL
* Basic fractals and fractal parametrization
* Depth-buffer exactness and reproducibility
* Separation of content generation and content illustration
* General OpenGL practice

The first version will, for simplicity, not work with threads or
multiple contexts, but rather be completely serial, however, be ready
for separation. In a second step content generation is moved into a
second context and thread for asynchronous generation and highly
performant rendering. This will then be the end of the exercise.