Correct `dependent: :destroy` for CIPs

www.agileplannerapp.com/boards/173808/cards/8853

there's a `dependent: destroy` on organisations to destroy associated corporate information pages when the organisation is deleted. in spite of that few orphaned CIPs exist: 336462, 336498, 363483. included data migration gets rid of these orphaned corporate information page editions and documents.

there are changes in 2 places to fix this issue:

0. `dependent: :destroy` on `corporate_information_pages` association only destroys the record in the join table and not the corporate information page edition. so the fix is to have an explicit `before_destroy` to clean corporate information editions and documents.

0. callbacks are invoked in the order in which they're declared. if the `before_destroy` to destroy corporate information gets registered before the `:edition_organisation, dependent: :destroy` this will work. else, when the callback tries to destroy related corporate information pages it won't be able to fetch the related corporate information editions because the linking record is gone.