Use collective.deletepermission

This pull-request integrates collective.deletepermission.
The `Delete objects` is mapped to "view" and `Delete portal content` to "delete".

@maethu I'm not quite sure if that is a good idea.
Mapping `Delete objects` to "View" will cause Anonymous to have this permission.
Although collective.deletepermission *should* take care that this permission alone is not enough
it is still a security risk (e.g. when collective.deletepermission doesnt't do the job after a plone update).
But I'm not sure how to map it differently so that it works.

Should we maybe not manage `Delete objects` in the workflow at all?

/cc @phabegger