FIX: avoid wipe tower conflict with objects

Use a more accurate way to estimate wipe tower:
1. read wipe configure from front-end (the positions may be different at
different plates).
2. when depth is unavailable, use all materials to estimate depth (the
estimated wipe tower may be larger than the actual generated one).

Change-Id: I42ffd03d9817b57f5023a6820cda0032509c6fe5
(cherry picked from commit 77ba9757023afb9160c996eeea6ead8a27b50ce4)

src/slic3r/GUI/GLCanvas3D.hpp

@@ -1058,6 +1058,9 @@ public:
 
     bool make_current_for_postinit();
 
+    //BBS
+    Points estimate_wipe_tower_points(int plate_index) const;
+
 private:
     bool _is_shown_on_screen() const;