Fix user form

* fix issue with checkbox on user form
* use consistent style for const char pointers
* use unique hostname by default

factory_settings.ini

@@ -3,7 +3,8 @@ build_flags =
     ; WiFi settings
     -D FACTORY_WIFI_SSID=\"\"
     -D FACTORY_WIFI_PASSWORD=\"\"
-    -D FACTORY_WIFI_HOSTNAME=\"esp-react\"
+    ; if unspecified the devices hardware ID will be used
+    ; -D FACTORY_WIFI_HOSTNAME=\"esp-react\"  
 
     ; Access point settings
     -D FACTORY_AP_PROVISION_MODE=AP_MODE_DISCONNECTED