Allow undeletion of items

[matthiku]

As plan items can contain quite some important information but an authorized user might accidentally or prematurely delete items.

Using Laravel's soft-deletes, it would be possible to recover them.

That means another method is needed in the items controller to show and undelete those items.

[matthiku]

When items are only "soft-deleted", it is not longer possible to delete a whole plan as the items still exist in the database. We need to add an option to show the "trash can" for that plan and a button for the admin to finally empty that trash can. Only then the plan can be deleted.

[matthiku]

How can I show both current and deleted items using the same code? (in items.blade.php)
How can I combine two result sets?

[matthiku]

Done with ability to restore items and perm delete them
changed: plan.blade, items.blade, itemcontroller, routes, helper