We should add appHistory.reload(), and probably subsume appHistory.navigate(options)

[domenic]

As part of #67, @jakearchibald, @annevk, @smaug---- and I were thinking about how to allow developers to express reloads with app history, so that they could stop using location.

You could currently do appHistory.navigate(appHistory.current.url), but this is not very explicit. Also, doing this fails to set the "reload-triggered navigation" flag which is visible to service workers, or set the navigationType visible to navigation timing.

So adding something like appHistory.reload({ state, info }) makes sense.

But then, once we have that, we probably don't need appHistory.navigate({ state, info }) anymore. Which is good, because that method was always a bit confusing.