Options:
* When sending updated options, there is no easy way to find which option has
  changed.

General:
* Pages have no way to act on the navigation. This is a general issue which is
  illustrated by the fact that when a page wants another page to be opened, it
  can't communicate easily with the parent navigation.
  This is also an issue for starting downloads.

Browser:
* Improve the concept of navigation by having a link between pages (i.e. page X
  has been created by page Y).
* Implement splits.
