Fixed SCAD and Updated

Scad source was missing the line PC_H = 13;

Added rendering options and removed static $fn assignments.

Added ability to use a parameter to select rendering pin/plug/both.

Minor cleanup of differences for preview view.

.gitignore

@@ -0,0 +1,6 @@
+*~
+*.tar*
+*.new
+*.bak
+out.*
+[._]*.sw[a-p]