Sometimes Clipper produces a polyline with more than 2 points when
clipping a line with a polygon or a set of polygons. We hope the intermediate
points are collinear with the line, so we may just ignore them.
1) Removed the already commented-out scaling / unscaling when doing
"safe offsetting"
2) Removed some of the "safe offsetting" at calls where it never was used.
3) Reworked Clipper & ClipperUtils to pass Polygons / ExPolygons / Surfaces
as input parameters without conversion to ClipperLib::Paths. This
should save a lot of memory allocation and copying.
4) Reworked conversions from ClipperLib::Paths & PolyTree to Polygons /
ExPolygons to use the move operator to avoid many unnecessary allocations.
5) Reworked some "union with safe ofsetting" to "offset_ex", which should
be cheaper.
Fixed some issues in internal anchors of the Adaptive Cubic infill.
The ugly and dangerous implicit casting operators in Line, MultiPoint,
Polyline and Polygon were made explicit.
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.
Changes in SupportMaterial.cpp, TriangleMesh.cpp and 01_trianglemesh.t
are yet to be merged.
WIP: Refactoring of layer height editing.
Removed layer_height_ranges from PrintObject, as the Print/PrintObject
now hold their copies of Model/ModelObject.
