Firmware 2.1.7 (WiFi txPower read/write in web interface)

WiFi txPower can now be read and set via the web interface.
It defaults to 19dB(m) which also is max tx power.
If the device is restarted due to BROWN_OUT (stated in reset reason rr in config message), the txPower is decreased one step.
Min tx power is 5dB(m).