Add support for 1.2" 4-Digit 7-Segment Displays

[caternuson]

Add support for 1.2" 4-digit 7-segment displays with I2C backpacks, like:
https://www.adafruit.com/category/103

Current library only supports the 0.54" versions which have a slightly different segment arrangement.

[caternuson]

Done with #18