Arcade Cabinet RPi

I decided to redesign the awesome cabinet made by @JCriotz.

The main reasons where:

* ability to install the raspberry pi at the back instead of the bottom of the cabinet
* have a different rear panel for different outlets
* have support for the 7" Waveshare HDMI screen I already had by hand

The rear panel is designed to support:
* 2 x Adafruit 908 USB A [https://www.adafruit.com/product/908]
* 1 x Adafruit 909 Ethernet [https://www.adafruit.com/product/909]
* 1 x Adafruit 3258 Mic