/sprints/X/+specs and /sprints/X/+assignments pages are almost identical

<https://launchpad.net/sprints/uds-mtv/+specs> is almost identical to <https://launchpad.net/sprints/uds-mtv/+assignments>; the only functional difference is that the former has a "Release/Series" column, while the latter has "Drafter" and "Approver" columns.

To reduce confusion, the two pages should be combined. If page width is an issue, either the listing should not use a table, or it should have checkboxes for showing/hiding columns (using JavaScript if present).