DatePicker is not working
You do not have to include all of that jquery libraries: Drupal core has that libraries. You can just include any jquery.ui library with drupal_add_library('system', 'ui.datepicker') or another library which you want to include. Then, in your JavaScript file, you can write something like this.

(function ($) {
  Drupal.behaviors.custom_js = {
    attach: function(context) {
      $('#YOURID input[type="text"]').datepicker({
        showOn: "button",
        buttonImage: Drupal.settings.basePath + "sites/all/themes/YOURTHEME/images/calendar.png",
        dateFormat: "dd-mm-yy",
        showAnim: "slideDown",
        buttonImageOnly: true
      });
    }
  };
})(jQuery);


If you want to use the datepicker with the form API, you have to change the type element to 'date_popup'.