Allow setting of outline on nodes the user may edit

Documentation editing on Drupal.org would be a lot easier if users could set the weights of child nodes in one location, rather than have to edit each child node.
In other words, see admin/content/book/NID if they have the permission to edit node NID, though this could probably do to be accessible from a tab on that node.

This doesn't look like a big change in the way access works in this module: _book_outline_access should consider if the user has edit access to that node and let that take priority.

However, this is simple only because Drupal.org has open editing. On a site that doesn't, we'd have a situation where a user may change the weight of child pages that they might not have permissions to edit.
Is this suitable?
The alternative would be to add a permission 'edit child outlines' which allows this access.