espalarm Code

Implement basic stuff for AHT20 sensor.
Workarounds for esp-idf bug with not C++-safe include files (dirent.h).

Revert send-again changes.
Minor tweaks to make temperature and boot message visible.

Second attempt at resending a reply

The LWIP layer doesn't appear to know IP-MAC mapping when we process the first packet
from a node, so initial info gets lost unless we transmit it twice. Doing just that now.

Partially working display for Temperature

Try to use the Temperature module without the Weather module.
Shift GTWT02 from Weather to Temperature, meaning it's now treated the same as a sensor (e.g. MCP9808 module hooked up to the esp).

Upgrade to arduinojson v6.
Small bugfix in Peers (reply to keepalive was misinterpreted).

Replace ArduinoJson v5 in libraries/ by ArduinoJson v6 in components/ .

Remove or document dependencies on Arduino.h

Small changes