'Add the item src_name in src_category to the User category
dest_category. Any leading \'@\' is removed'

def do_add_item_to_user_cat(self, dest_category, src_name, src_category):

    db = self.library_view.model().db
    user_cats = db.prefs.get(u'user_categories', {})
    if (dest_category and dest_category.startswith(u'@')):
        dest_category = dest_category[1:]
    if (dest_category not in user_cats):
        return error_dialog(self.tags_view, _(u'Add    to    User    category'), (_(u'A    User    category    %s    does    not    exist') % dest_category), show=True)
    add_it = True
    if (src_category == u'news'):
        src_category = u'tags'
    for tup in user_cats[dest_category]:
        if ((src_name == tup[0]) and (src_category == tup[1])):
            add_it = False
    if add_it:
        user_cats[dest_category].append([src_name, src_category, 0])
    db.new_api.set_pref(u'user_categories', user_cats)
    self.tags_view.recount()
    self.user_categories_edited()
