domoticz: refactoring

Common functions moved into namespace domoticz { ... }
Module functions moved into namespace { ... }

Remove templates and favour simple function for nvalue & svalue formatting,
and also use ArduinoJson for the JSON serialization.

Detach lights from the 1st relay, introduce `dczLightIdx`
Use named channel functions instead of counting channels manually.
Try to migrate the old settings.

Introduce stronger type for Idx to avoid entity id vs. domoticz idx confusion in function arguments,
since both are numeric and there's no distinction besides the name itself.

code/espurna/config/version.h

@@ -21,5 +21,5 @@
 #endif
 
 #ifndef CFG_VERSION
-#define CFG_VERSION             9
+#define CFG_VERSION             10
 #endif