WebNode's history support has several problem:

1) While WebEngine.back() seems to work, WebEngine.forward() doesn't do anything
2) Calling back() and forward() for initial WebEngine leads to crash

Moreover I suppose we need to have a better management of history changes in WebEngine,
currently there is no way to detect if the history is empty or not
which prevents users from implementing history navigation with WebNode

the best solution is to support the API similar to what HTML5 specifies:

http://www.w3.org/TR/html5/history.html#the-history-interface