Blur and bounding box

Hello,

I'm using both UI and command line versions of the exporting functions to
generate web interfaces elements in PNG. Something difficult to handle
right now is to export an object with blur pixels being out of the bounding
box. Take the example of a button with a simple shadow under it: if the
shadow has some blur effect on it, all blur-generated pixels out of the BB
are just cut out of the exported bitmap.

There could be an option to extend the bounding box of an object/group so
that it includes all the blur associated to it. That option could only
apply to exports or could be included in the object/group properties.