Avoid API confusion, rename borderInsets to fetchInsets

In KoShape there is both a border and a shadow that you can set,
both of which have insets. A confusing moment ensued when asked
asked the question why there was no shadowInsets() but there is
a borderInsets().

Turns out that the answer is that one occupies space insde and the
other outside the boundingrect. So lets avoid the API naming
'border' and thus avoid having to know about this distinction.

Also change the API slightly to avoid copying mania, instead
pass in the object and just fill it.