4892: ims_import.php: fix several issues that cause import failures

4892: ims_import.php: fix several issues that cause import failures

  * Weblinks: correctly locate link resource file by replacing incorrect
     $content_info['href'] with $content_info['file'][0]
  * Weblinks: ensure weblink file has been parsed correctly before assigning variables
  * capture and use result from $contentDAO->Create()
  * undefined indexes: $items[$current_item_id], $items[$dependency_ref],
     $items[$content_info['parent_content_id']], $items[$item_id]['type']
     $content_info['type'], $content_info['dependency'], $content_info['href'], $content_info['new_path'],
  * undefined variables: $ext, $full_filename, $lti_offset[$content_info['parent_content_id']],