Reorganise shaders

shader/twoD/ellipse.frag

@@ -0,0 +1,13 @@
+#version 430 core
+in vec4 gColorC;
+in vec4 gColorE;
+in vec2 gBoundingBox;
+
+out vec4 fColor;
+
+void main()
+{
+  float d = dot(gBoundingBox,gBoundingBox);
+  if ( d > 1) { discard; }
+  fColor = mix (gColorE , gColorC, d);
+}