Center content on flatpages

[ingraso]

If a committee or group has less than 5 members, there is a lot of empty space on the right side of its flatpage. This is because of an alignment to the left, instead of centering. This is the case for all the flatpages ("Om Abakus"), but it is much more visible when there are few members. Examples can be seen for the revue groups PR-revy and Dans. An example of how it should look is the Band page.