Completed design for v2.

models/common/metric_bolt_functions.scad

@@ -0,0 +1,9 @@
+
+function get_metric_bolt_head_height(size) = size;
+function get_metric_bolt_head_diameter(size) = size * 2;
+function get_metric_bolt_washer_diameter_safe_working_clearance(size) = 
+    (size < 20) ?
+        4 * size
+    :
+        3 * size
+;