[cutting_optimizer] handle attached paths in groups

[vmario89]

If we have paths, which contains other elements like inner unclosed polygons or patterns, we want to keep them after nesting. but this is not possible using cutting optimizer. we could try to add some logic to calculate the transformation of the nested items in relation to their previous, unnested position. maybe we could use those transformations to re-align the attached polygons/lines to the elements then.