Add support for checking permission of page's parents.

Allows you to optionally check the edit permission of each of the page's parents. 

This can greatly reduce the number of pages which need to be added to a user's editable-pages list as it allows only the page acting as the container of a group of pages to be tagged as editable.

So, instead of this...

    /
    |- John's Tags
    |         |-- Soccer (added to John's list)
    |         |-- Rugby ( ditto )
    |         |-- Skiing ( ditto )
    |...

You only have to add the "John's Tags" page to user John's editable-pages list and all the child pages can now be edited by him.