WIP GCode/SmoothPath.cpp,hpp cache for interpolating extrusion path with arches.
Removed Perl test t/geometry.t, replaced with C++ tests.
Refactored ExtrusionEntity and derived classes to hold extrusion attributes in new ExtrusionFlow/ExtrusionAttributes classes.
Reworked path ordering in G-code export to never copy polylines, but to work with a new "flipped" attribute.
Reworked G-code export to interpolate extrusion paths with smooth paths and to extrude those smooth paths.
New parameters: arc_fitting, arc_fitting_tolerance
Renamed GCode class to GCodeGenerator
Moved GCodeWriter.cpp/hpp to GCode/
Moved Wipe from from GCode.cpp,hpp to GCode/Wipe.cpp,hpp
Moved WipeTowerIntegration from GCode.cpp,hpp to GCode/WipeTowerIntegration.cpp,hpp
New variant of douglas_peucker() to simplify range of iterators in place.
Refactored wipe in general and wipe on perimeters / hiding seams.
WIP: Convert estimate_speed_from_extrusion_quality() and its application to smooth paths.
WIP: Cooling buffer to process G2G3, disable arc fitting for filters that cannot process it.
so that the ordering code at G-code export may work directly with
pointers to PrintInstances instead of with pair of <PrintObject, copy idx>.
Also the PrintInstance knows its source ModelInstance, which allows
sorting of PrintInstances for sequential printing in the order
they appear in Plater's object list.
for islands with another islands in their holes.
Improvement of chaining of infill lines for 3D honeycomb, Gyroid and
Honeycomb infill: New TSP chaining algorithm is used.
producing better shortest path estimate than the "closest next neighbor"
heuristics. The new greedy algorithm utilizes KD tree for closest
end point search, and builds a graph to detect loops.
PerimeterGenerator newly uses the optimized TSP algorithm.
ExtrusionEntity has been refactored / simplified.
