minor typos in primer

Hi,

I am browsing through Primer (http://www.w3.org/2007/OWL/wiki/Primer) 
and found a few very minor typos.

- a few places (in Turtle syntax) still use owl:propertyChain instead of 
owl:propertyChainAxiom

- In Section 6.3, we have (for Turtle Syntax) 

   :Person owl:hasKey :hasSSN 

  It probably should be :Person owl:hasKey  (:hasSSN)   
 

- In Section 7, "This way, we can e.g. express" looks a bit strange.


Cheers,

Zhe