irregular solver will not generate compact result when item-item-minimum-spacing set to non-zero value

Hi Florian，

Nice project & awesome code!

I did check the code, the problem I described in the title is probably due to:
 - how the inflate(LengthDbl value) was achieved: it will extend item_item_minimum_spacing in all direction of the trapezoid shape
 - BranchingScheme::update_position: it will not move the minimum required distance when overlapping detected

Please correct me if I'm wrong.