FIX: rewrite per-object printing order logic

1. Previous logic can't guarantee left-to-right printing order, so
   toolhead may crash on the right side. In the new algorithm printing
   order is guaranteed.
2. Clearance radius should be the max of 3 directions (left, bottom,
   up), not including right, otherwise collision may happen on bottom or
   up directions.
3. Add is_extrusion_cali_object property to handle extrusion brim
   overlap better.

Change-Id: I44868b9925d983f5cca0c31d35dfa28d895fadbf

src/libslic3r/PrintConfig.hpp

@@ -824,6 +824,7 @@ PRINT_CONFIG_CLASS_DERIVED_DEFINE(
     ((ConfigOptionFloat,              extruder_clearance_height_to_rod))//BBs
     ((ConfigOptionFloat,              extruder_clearance_height_to_lid))//BBS
     ((ConfigOptionFloat,              extruder_clearance_radius))
+    ((ConfigOptionFloat,              extruder_clearance_max_radius))
     ((ConfigOptionStrings,            extruder_colour))
     ((ConfigOptionPoints,             extruder_offset))
     ((ConfigOptionBools,              reduce_fan_stop_start_freq))