Visualization - Provide gamma correction in OCCT ray-tracing core

To provide right perception of rendered image it must be converted to non-linear space using gamma-correction filter (gamma = 1.0/2.2). On the other hand, textures are already converted, and thus require inverse gamma correction (gamma = 2.2) before shading calsulations. Please note that gamma-correction should be provided as option, because we need to support OpenGL-like output.