fix some things: do not use onReady Event to fill page with content because after loading content from history this evenbt also might be triggered but we don't want to load entities after going back to history. so we trigger a custom event after loadIntoSection() has been finished. we must unload its event handlers otherwise events may be called twice. fix unit test ContentTest by adding PageHistory to spec.html. add page history and override default event handler of hardware bak button of phone