Refactored showNotFound into notFoundView

I'm working on the router! And I noticed some logic got confused. 

`showNotFound` returned a view that was yet to be opened. One bit of code did this, the other code that used the function assumed the view would be opened by `showNotFound` itself. The name does hint at it. That's why I changed the name to `notFoundView`, hinting at a view that is created but yet to be opened, and corrected the current uses of `notFoundView` (where originally no view would be opened at all).

The cleanest would be that only top functions would be allowed to `@openView`, since now responsibility does tend to get confusing. We're good for now though.