Update Event hooks list

[j-a-pope]

The event hooks list is copied over from the old boxbilling documentation.

• Check that any of the listed hooks have not been deprecated and remove from the list if they have.
• Add new hooks (after PR has been merged) - onBeforeAdminUpdateCore, onAfterAdminUpdateCore, onBeforeAdminUpdateExtension and onAfterAdminUpdateExtension
• Create a more coherent list order with sections.