add tonemapping shaders

shader/ToneMap/HejlRichard.glsl

@@ -0,0 +1,7 @@
+// Hejl Richard tone map
+// see: http://filmicworlds.com/blog/filmic-tonemapping-operators/
+vec3 ToneMapping(vec3 color)
+{
+    color = max(vec3(0.0), color - vec3(0.004));
+    return (color*(6.2*color+.5))/(color*(6.2*color+1.7)+0.06);
+}