Create an 'archive' action for reservations

[squidgetx]

Via #526, in the rare case that an administrator needs to put away a reservation (to free up equipment items) but would like to preserve history, there should be a button in place of mnage reservations on the reservation show page that sets a checkout and checkin date appropriately so that the reservation can view as 'returned'

[dgoerger]

wait, so, bogus checkout and checkin dates? If we do that, perhaps we could set it as checked_out = checked_in, since afaik the database is fine with length-zero reservations? We'd want a note to be added to the reservation to explain that this is what happened, too.

[squidgetx]

Yeah that seems like it'd be the thing to do. Choose your poison

[orenyk]

I would set checked_in as the date the reservation was archived, but this should be pretty straightforward, especially with the refactoring of :checkin (#666).