Default "Centre in box" preference not respected by the image editor

[GoogleCodeExporter]

If I select "centre in box" this is not transfered when I insert the overlays 
and the text is not centered. I can edit each overlay and then check the box 
"center in box" again, but it would be better to do this only once in the 
settings.

Also changing the size of the box by dragging is rather difficult.

Original issue reported on code.google.com by [email protected] on 10 Jan 2013 at 3:48