Create uninstall-delete-piwik-directory.php

This is a copy from Piwik

Usage:

1. Upload this file to root (normally root folder, or other path that contains 'piwik' folder, which is above the 'piwik' directory)
2. Execute this file
3. It should remove 'piwik' folder

Alternative:
Usa FTP remove 'piwik' folder

Notes:
This file removes 'piwik' folder only. You need to delete piwik-related tables from database and tracking code in HTML pages as well to entirely remove piwik.