Improve graphs

Improve graphs

The graphs are using an iframe and PNG images where the resolution
did often not fit and the browser had to resize the image. That
led to blurred fonts and hard to read graphs.

This patch increases the size of the box and the image. With that
higher resolution resizing should not be too much of an issue, but
since the sizes of the iframe and image have been aligned should
not even be necessary.

Reported-by: Marcel Lorenz <marcel.lorenz@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>