Build and ajax plugin not work

You never enqueued the ajax_init in a function. Also you can use plugins_url() and split into two functions with a shortcode, like this:

(not tested)

<?php 
/*
Plugin Name: Ajax Plugin
Description: Plugin for adding ajax
Version: 1.0
*/
/*-------------------------------------------------------*/
/* Register Scripts
/*-------------------------------------------------------*/
add_action( 'wp_enqueue_scripts', 'ajaxp_init' );
function ajaxp_init(){

    /*
    * registro del script
    */

     wp_enqueue_script('jquery');

     wp_register_script( 'jfile_general_js', plugins_url('pablowishlist.js', __FILE__));
     wp_enqueue_script('jfile_general_js')

}
/*-------------------------------------------------------*/
/* Add shortcode
/*-------------------------------------------------------*/
add_shortcode('ajaxplug','jfile_manager');
function jfile_manager() {
        global $post;

        wp_localize_script('jquery_no_conflict','MyAjax', array(
            'postId' => $post->ID,
            'action' => 'ajaxp_add_wishlist'
        ));
}