Fix issue with null camera references.

Since the initialization order changed there was an issue with the
camera being accessed before it was initialized.
Added some extra asserts.

For things that shouldn't be null.
Measure time taken to load page.
Load nearby pages directly.
Use a strategy to load pages close to camera.

This is a better solution than trying to preload certain pages.
Remove obsolete method.

No need to do this now when we have do it in a superior way through the
page load strategy.