Sideband & RNode Bluetooth and Display Support

[markqvist]

Just as a heads up to anyone who didn't see it yet:

The RNode Firmware now has full Bluetooth and display support. All supported devices with built-in displays work out of the box, as soon as they have been flashed. You need to update to at least rnodeconf version 0.2.0, which is now included directly in the rns package, to flash it.

For T-Beam devices, you can connect an external SSD1306 OLED display to the GND, 3V3, SCL and SDA pins, and optionally digital Pin 0 as the reset line, if your display needs a physical reset line. The T-Beam version of the firmware expects the display to use I2C address 0x3D. If displays with alternative addresses are in use, I can add a switch in the firmware build system for those as well.