fixed ob_end_flush() error problem in  some not very smart frameworks

Some frameworks like Drupal are calling ob_end_flush() without checking that output buffer is not marked as PHP_OUTPUT_HANDLER_FLUSHABLE, so they get E_WARNING. Because PhpConsole now is using more smart communication protocol that is not so critical about headers flushed before script shut down, so there is no more need to use not removable ob_start().