Screen Space Reflections effect, enhancements to GLSL API for effects

[DP News-Robot]

With many thanks to Kagamma (Trung Le), we now support screen-space reflections in Castle Game Engine! It is a cool technique that generates reflections completely in screen-space, using color and depth buffer information to look for the reflected color. It is trivially easy to use, just toggle TCastleViewport.ScreenSpaceReflections boolean. As we don’t have material information …