Don't display the "Create a new wiki" link for users without the right to create a wiki

Steps to reproduce:

1. Login with a normal (non Admin) user
2. Create a new page and use

   {{wikis/}}
   

   as its content

Notice you also have a link to "Create a new wiki", but if you click on it and fill in the required fields on the 2 wizard steps, you'll eventually get an error similar to this one:

Wiki "test" creation failed: org.xwiki.security.authorization.AccessDeniedException: Access denied when checking [createwiki] access to [Wiki xwiki] for user [xwiki:XWiki.manuel].

In the UI you don't have a link to Add a new wiki unless you have the "createwiki" right.