Optics: Gaussian bi-variate shape error for concentrator optics added.
Sources: Buie Sunshape discretisation implemented.
Models: Moved the 4 parameter cavity in models and cleaned it a bit. Fluxmap works but has some boundary effects to be cleaned.
Surfaces: added a 1e-10 tolerance to the positive test on flat surfaces intersection to solve a floating point precision error at this level.
Rendering: Added a rendering class to use CoIn more easily. Might not be optimal but works for now.