WIP: Reworked the infill generator to merge areas with the same

properties.

Note for Vojtech:
Review src/libslic3r/Fill/Fill.cpp once again,
add test for G-code generator properties (extrusion speed, cooling?)

Fixes Modifier slice/move efficiency #1005

src/libslic3r/Fill/FillBase.hpp

@@ -70,6 +70,7 @@ public:
 
     static Fill* new_from_type(const InfillPattern type);
     static Fill* new_from_type(const std::string &type);
+    static bool  use_bridge_flow(const InfillPattern type);
 
     void         set_bounding_box(const Slic3r::BoundingBox &bbox) { bounding_box = bbox; }