Anonymous posting and some improvements

Hi, i've added a new feature to ploneboard:
with a checkbox in control panel, we can enable anonymous users to sign their comments/discussions with a name instead default "Anonymous".

I've also replaced "getLastCommentUrl" index/metadata with "getLastCommentId". It's not the best thing storing an url in the catalog (especially If we have different urls for frontend and backend). If we store the id, we can build the url dynamically.

Another little thing: i fixed i18ndude script and updated translations