re-org docs/

docs/img_prep/nut.scad

@@ -0,0 +1,16 @@
+/*
+Create nice previews for documentation
+
+:Author: Adrian Schlatter
+:Date: 2019-04-10
+:License: 3-Clause BSD. See LICENSE.
+*/
+
+use <threadlib/threadlib.scad>
+
+type = "M12x0.5";
+turns = 10;
+Douter = 16;
+higbee_arc = 45;
+
+nut(type, turns, Douter, higbee_arc=higbee_arc);