refactor - introduce config folder, and other misc changes

helper/apply.scad

@@ -0,0 +1,35 @@
+// Modules for apply pattern
+
+module apply_p() {
+  union() {
+    children(0);
+    children(1);
+  }
+}
+
+module apply_n() {
+  difference() {
+    children(1);
+    children(0);
+  }
+}
+
+module apply_pn() {
+  difference() {
+    union() {
+      children(0);
+      children(2);
+    }
+    children(1);
+  }
+}
+
+module apply_np() {
+  difference() {
+    union() {
+      children(1);
+      children(2);
+    }
+    children(0);
+  }
+}