Addind up and down arrows to modify the order (priority/sequence) of a list dynamically

In some lists, like BOM, SO, contacts (base_contact), pricelist, etc... it could be useful or needed to specify an order. This can be done today by adding manually a sequence. Unfortunately you've to type it manually in the field, this could be quite an heavy job, and not at all user friendly. It would be a nice enhancement to have the possibility to switch lines in the list using arrows (up and down). This is already implemented for example in the view editor of the web interface. It would be useful to have it in other interfaces and both in GTK and web client.