psql: use `created` colum to sort by creation: `item_id` was used to sort by creation because it correspond to it and it's slighly more efficient, but #398 raises the use case of manually modified database to import items. The column has been changed to suit this use case, and `item_id` is now always added as last order, in case of date conflicts. This patch extends a contribution from Stephen Paul Weber (Singpolyma) from the ticket mentioned below. fix: 398

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e289636ccc4f9e3690879aaf7b9bb5f2674c3fc8 idavoll-0.7.3
560b6cdc50b20d7590a70b0311d4781e3296c589 0.1.0
232002e132dbf9c7563d9f78f4b5e2bcdc2764de 0.1.1
642dffb9d6f1e7b2e7d5e9cb6ba17b6950fdf0bb 0.2.0
0861da6975b57dcaa1c69b2833232fe191346f87 0.3.0