Add mqtt_uns_structure configuration and uninstall functionality (#196)

- Prompt user for mqtt_uns_structure during installation and update src/config.py accordingly.
- Implement uninstall function in remote_install.sh to remove the rpi-mqtt-monitor directory, cron job, and systemd service.
- Update rpi-cpu2mqtt.py to utilize mqtt_uns_structure for state topics, ensuring proper MQTT topic structure.
- Modify config.py.example to include mqtt_uns_structure with a default empty value.

Co-authored-by: Sam Blackman <sam@samuelblackman.com>

install.sh

@@ -107,6 +107,13 @@ mqtt_configuration(){
     TOPIC=rpi-MQTT-monitor
   fi
   sed -i "s/rpi-MQTT-monitor/${TOPIC}/" src/config.py
+
+  printf "Enter mqtt_uns_structure (default is empty): "
+  read UNS
+  if [[ -n "$UNS" && ! "$UNS" =~ /$ ]]; then
+    UNS="${UNS}/"
+  fi
+  sed -i "s/mqtt_uns_structure = .*/mqtt_uns_structure = '${UNS}'/" src/config.py
   
   printf "Do you need to control your monitors? (default is No): "
   read CONTROL