Add setup-tools uninstallation test.

The plone/zope quickinstaller seems to uninstall certain configuration by itself (from some kind of metadata created while installing), even when not defined in an uninstall profile.

This may result in a discrepancy between uninstalling over ``prefs_install_products_form`` and applying the uninstall-profile in ``portal_setup``.

This PR adds a second test that ensures that setup_tool uninstallation reverts plone to the same _"clean"_ state as quickinstaller uninstallation.