Suggestion: add a "Serial" library à la existing one in "Java" mode

[q2dg]

I've found this https://github.com/inventit/processing-android-serial , it could be a start My reasoning is explained here: https://github.com/inventit/processing-android-serial/issues/9#issue-167738576

I've also found this other libraries, but they are only for Java, not for Processing: https://github.com/felHR85/UsbSerial (anyway I've requested a port here: https://github.com/felHR85/UsbSerial/issues/63 ) and https://github.com/mik3y/usb-serial-for-android (requested port here: https://github.com/mik3y/usb-serial-for-android/issues/148#issue-167800350 )

Thanks a lot