re-org docs/

docs/img_prep/flexible.scad

@@ -0,0 +1,22 @@
+/*
+Create nice previews for documentation
+
+:Author: Adrian Schlatter
+:Date: 2019-04-13
+:License: 3-Clause BSD. See LICENSE.
+*/
+
+use <threadlib/threadlib.scad>
+
+type = "G1/2-ext";
+turns = 5;
+higbee_arc = 20;
+
+thread(type, turns, higbee_arc=higbee_arc);
+
+specs = thread_specs(type);
+P = specs[0]; Rrot = specs[1]; Dsupport = specs[2];
+section_profile = specs[3];
+H = (turns + 1) * P;
+translate([0, 0, -P / 2])
+    cylinder(h=H, d=Dsupport, $fn=120);