* 1. Remove all global include_directories.
* 2. Move 3d party dependencies from src to budled deps if possible.
* Unify and enforce one way of including headers:
e.g. #include "libslic3r/GCode.hpp" vs #include "GCode.hpp"
(always use the "libslic3r/GCode.hpp" option).
* Make all dependencies (also header only) a cmake target.
Especially in cases when the object is composed only of 2 external perimeters and 1 or 2 internal perimeters, the order of perimeters wasn't optimal and differed from the Classic perimeter generator. That caused unnecessary long travels before the external contour was printed.
The ordering of perimeters is slightly inspired by the latest changes in CuraEngine.
