Added simple JSCAD modifier helper

Simple cube oriented around the center with a parametric interface. Just copy/paste into openjscad.org and hit shift+enter.

utils/modifier_helpers/layer_generator.jscad

@@ -0,0 +1,19 @@
+// title: Layer_generator
+// written by: Joseph Lenox
+// Used for generating cubes oriented about the center 
+// for making simple modifier meshes.
+
+var width = 100;
+var layer_height = 0.3;
+var z = 30;
+function main() {
+    
+    return cube(size=[width,width,layer_height], center=true).translate([0,0,z]);    
+}
+function getParameterDefinitions() {
+  return [
+      { name: 'width', type: 'float', initial: 100, caption: "Width of the cube:" },
+      { name: 'layer_height', type: 'float', initial: 0.3, caption: "Layer height used:" },
+      { name: 'z', type: 'float', initial: 0, caption: "Z:" }
+  ];
+}