Added support for UNO R4 WiFi and additional printers

This release adds several improvements contributed by other developers (e.g. cleanup of supported printer list). I also added specific support for the Arduino UNO R4 WiFi board. It has less RAM and I corrected the font data to be const so as not to use up RAM space. I also added support for a new named printer which behaves the same as the "MTP-2" type.