* Colorize the logging messages of different level with different colors
* Also add a different icon for each message

Add "updateTaskStatus()" to update the "#task-status" element.

Also add function "getServerTaskStatus()" to get the task status from
the server.

* Fix the validation for some "input[type=number]" element;
  By default, the number type input only accept *integer*. By setting
  the 'step="any"' attribute, the float numbers are also valid.
* Add form input validation styles for ":valid" and ":invalid" pseudo
  classes.

* Rewrite "configs.js" to be more modular and generic
* Bind functions to button click event
* Implement the function to set form fields to given configuration data
* Implement the function to reset server-side configurations
* Implement the function to load user configuration file on server
* Implement get the configuration data from the server

Also add a global variable "ws_reconnect" to control the timeout between
reconnection and the maximum reconnection times (default: 100).

Add a label to the header banner to show the WebSocket support status
and connection status.