Enhance DS18B20 plugin to handle multiple sensors on same ESP32 pin

[Andrew49]

The current version (alpha v53) appears to need each DS18 to be connected to a different ESP pin. Attempts to use a common pin fail, the different sensor ROM addresses don't seem to be saved and both tasks display exactly the same value.
The enhancement would follow the behaviour of the ESP8266/ESP Easy, and would reduce the number of pins needed for multiple one-wire sensors, and also simplify wiring by enabling a common one-wire bus to be used.