Fire pre and post hooks for trash and restore of contacts

Problems:
1. Currently no hook is fired when restoring a contact from trash.
2. Also, the 'delete' operation is passed to pre and post hooks at two different times: when moving a contact to trash, AND when permanently deleting a trashed contact.

Proposed solutions:
1. This patch addresses item 1 by adding 'trash' and 'restore' operations for pre and post hooks.
2. This doesn't attempt to address item 2; a more complete solution will be – I suggest – to stop firing the hooks with 'delete' operation when sending contact to trash, and only use that op when permanently deleting the contact; but this raises backwards-compatibility concerns, so I'm not trying to address it here. So with this patch, these hooks are still called with 'delete' op upon trashing a contact, but now they're also called with the 'trash' op at that time.