edit/delete comments permissions

Hi, i forked @gyst 's branch (edit-comments-squashed) and made some changes:
- removed "delete own comments" from control panel. Now is managed by a permission "Delete Comments"
- relaunched i18ndude script and fix italian translations
- created an upgrade-step to update rolemap with new permission

I've also fixed test from "edit comments" behavior because doesn't works after recent product updates

Let me know if it's all ok, or i'm missing something.
P.S.: i've send my contributor agreement last week (for plone.org user "micecchi"), but i don't know when it arrives.