include Products.CMFCore in configure.zcml

Without this, it won't start on Plone4.1, because it doesn't know about the permission="cmf.ManagePortal".
See http://plone.org/documentation/manual/upgrade-guide/version/upgrading-plone-4.0-to-4.1/updating-add-on-products-for-plone-4.1/changing-dependencies-from-plone-to-products.cmfplone