cleanup show order and add search

An attempt to make the show order screen a bit cleaner. Search works in default, groups and articles view (listjs).
![cleaned_up_show_order](https://f.cloud.github.com/assets/503804/1940640/458bc2a4-7f7c-11e3-9a45-bc501805a341.png)

p.s. Multiple `tfoot`s in in one `table` are not allowed, so I moved these intermediate headings into the body, which had a nice side effect that listjs search showed the whole `tbody` when a row matched - exactly what I wanted.