Fix List.html Checkbox Column Width

This gets rid of the last span1 class in List.html and makes it more bootstrap 3 compatible. Also improves the look of the button column by removing the extra space on the right and centering the buttons.

Here's what it looks like with the update: http://imgur.com/sLZPg58

Here's what it used to looked like before: http://imgur.com/luYh4dr

It also centers the text so it still looks nice when there is only 1 element: http://imgur.com/EuloLbZ