FYI: some wiki tweaks

[Simon Michael]

Plone and Zwiki are each featureful products with their own view of the 
world; when you put them together I think it's important to turn off all 
non-essentials to reduce UI clutter and confusion. Less is more. 
Following some discussion on #ubuntu-doc, here's what I did, which I 
hope you will approve:

- restricted the content types allowed in the wiki to two: Wiki Page and 
Image. People were creating Documents instead of wiki pages and getting 
confused.

- made an add wiki page link at the top which is equivalent to the 
create form at the bottom of the page. It now sets the new page's 
parentage properly. I would have removed this link, but left it there 
for consistency with "add image".

- made the "issue tracker" and "filter issues" links go away, and 
rearranged the others a little

- disabled the contents tab (and plone folder listing view) for 
non-managers.

- disabled the aliases tab.

Cheers,
-Simon