Improved Low-Voltage Bracket

I remixed lilfonzy's Low-Voltage Bracket to make the arms stronger. I printed out his version and the arms were far too flimsy and broke quite easily. In this version the arms are an order of magnitude stronger and don't interfere with the overall design or shape.

**UPDATE:** I added the missing arms .stl (oops) and also made the model printable without supports! Yay! The screw hole edges are now tapered at a 45° angle so they're basically the perfect countersunk screw holes now.