Make a wb-claim-mainsnak element have a wb-snak instead of being one itself 

This is related to bug 62527. Also corrects template parameter comment order in
statementview.

Change-Id: I32ebe3b33e77c0f06a37e0c0779d6d2280db4f4d
Merge "Make a wb-claim-mainsnak element have a wb-snak instead of being one itself "