Smart water leak sensor

These smart sensors detect water leaks by measuring resistance between two contacts (two M3 bolts). If a water leak is detected:

* Local alarm goes off (loud piezo buzzer signals, blinking red LED)
* All other identical water sensors throughout the house also sound alarm (loud piezo buzzer signals, number of red LED flashes in a sequence = sensor ID of the sensor were the leak was detected). For this, WiFi and MQTT server are required
* Alarm is displayed in OpenHAB browser (or app) interface (on smart phones etc.). WiFi, MQTT server, and OpenHAB server are required.
* Email is sent to a predefined email address. WiFi, MQTT server, and OpenHAB server with the Mail action add-on are required.

After alarm goes off, pressing the button on any sensor will silence all alarms for predefined interval (30s by default). Only buzzer becomes silent, but the rest works as usual (water detection, red LED alarm, OpenHAB notifications, emails etc). After the predefined quiet time, if the wa