[sailfish-browser] Fix failing tst_webview

Reverts title change handling from DeclarativeWebContainer::onActiveTabChanged that was introduced in commit ad85e79d.

Adds title changed and urlchanged helpers so that we do not emit signals unnecessarily. 

CloseActiveTab does not trigger load anymore (SHA1 ad85e79dda). So, activatePage in test case.
What's the point of having &oldUrl in the signature if oldUrl refers to mUrl always?