Added ContourPoints and Threshold filters

orx-jumpflood/src/main/resources/shaders/gl3/threshold.frag

@@ -0,0 +1,13 @@
+#version 330 core
+
+uniform sampler2D tex0;
+in vec2 v_texCoord0;
+uniform float threshold;
+out vec4 o_color;
+
+void main() {
+    float ref = step(threshold , dot( vec3(1.0/3.0), texture(tex0, v_texCoord0).rgb ));
+
+
+    o_color = vec4(ref, ref, ref, 1.0);
+}