Replicator Strain Relief Upgrade Upgrade

A slightly improved version of a greatly improved means for terminating the extruder control umbilical. I took GeraldO's http://www.thingiverse.com/thing:21570 and added an undercut to the hooky portion, as he'd suggested, permitting the wires to escape more readily. I also added some fillets, just for fun.

To improve printing with the undercut up, I chamfered the counterbored hole's bottom.