#207 proper clipping for borders & padding

[Sarah Wilkin]

When adjusting the properties css.borderWidth or
css.padding the clipping property needs to be changed
as well.

For example if I have a 100x100 layer and add at 10px
border the clipping is still (0,100,100,0) so the
bottom and right sides are clipped off. Currently I'm
manually adjusting it so my layer displays correctly
but a fix would be much appreciated!