Reuse the existing DOM on entity page initialization

Changes to HTML (most of them have been introduced in earlier patches):
* wb-claimlists and wb-claims don't have a wb-listview class
* wb-claim-mainsnak has a .wb-snak child instead of being one itself
* wb-statement-rank has a .wb-rankselector child instead of being one itself
* Class wb-last is completely removed

Change-Id: Ibdaf655a23187ac1c3fc09c9e5ee69cf684834e6