Implement uninstall / use ftw.profilehook

- Use [ftw.profilehook](https://github.com/4teamwork/ftw.profilehook) instead of setuphandler for registering index.
- Implement an uninstall profile.

@buchi can you take a look?
`<five:registerPackage package="." initialize=".initialize" />` is required (and thus the empty `initialize`) for the uninstall to work (`Extensions/install.py`) :confused: