serre SVN

Split implementation in two pieces.

Moving old stuff to old/

Add almost unchanged versions (w.r.t. my esp32 code) of Firebase and CloudMessaging classes.

Cosmetic changes

Update doc about SNTP update

Small tweaks to code, update documentation

Ported my esp32 OTA code to this environment :-)

Next generation of this application : drop the MQTT and Arduino dependencies.

Add these versions here, historic versions are in github or its clone on https://sourceforge.net/p/serre/code/ .

add directory