NTP Timezone & Enable/Disable Setting (#80)

* quick and dirty WIP to investigate timezones, currently only building under esp8266 platform
much of the status stuff has been stripped for now, to test the concepts

* support set of common features across ESP32/ESP8266 WRT timezone and sntp
return dates as ISO format strings

* remove time library, and timelib fix which is no longer required

* fix the icons

* remove temporary changes to demo project

interface/.env.development

@@ -1,3 +1,3 @@
 # Change the IP address to that of your ESP device to enable local development of the UI.
 # Remember to also enable CORS in platformio.ini before uploading the code to the device.
-REACT_APP_ENDPOINT_ROOT=http://192.168.0.20/rest/
+REACT_APP_ENDPOINT_ROOT=http://192.168.0.29/rest/