Ooze prevention:

- remove the infinite skirt
- added 'idle_temperature' in Filament Settings as an optional parameter
- the logic is changed: if idle_temp is present, it is used,
  otherwise it uses the old delta value from Print Settings
- TODO: the optional parameter is not well supported in UI

src/libslic3r/Print.cpp

@@ -191,6 +191,7 @@ bool Print::invalidate_state_by_config_options(const ConfigOptionResolver & /* n
             || opt_key == "infill_first"
             || opt_key == "single_extruder_multi_material"
             || opt_key == "temperature"
+            || opt_key == "idle_temperature"
             || opt_key == "wipe_tower"
             || opt_key == "wipe_tower_width"
             || opt_key == "wipe_tower_brim_width"