fixes on ratio_over
fix Flow::extrusion_width (bad computation of first_layer_height)
fix enum visibility
moving test classes to prusaslicer test directory (wip)
all that because i was trying to write a test class for a modification in min_object_distance (and i didn't even start)
Implementation of 2-opt pairwise exchange iterative improvement
algorithm with an extension to a chain of segments, where
the chain of segments may get flipped during the exchange operation.
The 2-opt exchange algorithm may be quite slow.