Priority for wipe tower, Increased safety distance from bed edges.

* WipeTowerInfo class extended in plater (WipeTower) instead of GLCanvas3D
* Bed origin support in ModelInstance and WipeTower

src/libnest2d/include/libnest2d/libnest2d.hpp

@@ -68,7 +68,7 @@ class _Item {
         BBCache(): valid(false) {}
     } bb_cache_;
     
-    int binid_{BIN_ID_UNSET};
+    int binid_{BIN_ID_UNSET}, priority_{0};
     bool fixed_{false};
 
 public:
@@ -130,8 +130,12 @@ public:
     
     inline bool isFixed() const noexcept { return fixed_; }
     inline void markAsFixed(bool fixed = true) { fixed_ = fixed; }
+    
     inline void binId(int idx) { binid_ = idx; }
     inline int binId() const noexcept { return binid_; }
+    
+    inline void priority(int p) { priority_ = p; }
+    inline int priority() const noexcept { return priority_; }
 
     /**
      * @brief Convert the polygon to string representation. The format depends

src/libnest2d/include/libnest2d/selections/firstfit.hpp

@@ -62,9 +62,10 @@ public:
             placers.back().configure(pconfig);
             placers.back().preload(ig);
         }
-
+        
         auto sortfunc = [](Item& i1, Item& i2) {
-            return i1.area() > i2.area();
+            int p1 = i1.priority(), p2 = i2.priority();
+            return p1 == p2 ? i1.area() > i2.area() : p1 > p2;
         };
 
         std::sort(store_.begin(), store_.end(), sortfunc);