Wipe tower postprocessing, wipe tower block on 3D plate improved.

- it renders red with one egde as indeterminate, the front edge is where the wipe tower will start
- changing width changes depth of the block (as requested)
- the block shows the brim of the wipe tower
- after slicing, the block is rendered in usual dark green and takes the exact shape of the tower (also with brim)
- moving or rotationg the block after slicing does not invalidate the wipe tower (and hence the exact block dimensions are preserved)
- changing anything that invalidates the wipe tower reverts the block back to the "indeterminate" shape
- the block is not shown after slicing, if the wipe tower is not actually generated (printing single color object with the wipe tower enabled)

This required changes in the wipe tower generator, which now generates the tower
at origin with no rotation. Resulting gcode is postprocessed and transformed during
gcode export. This means the wipe tower needs not be invalidated when it is moved or rotated.

lib/Slic3r/GUI/Plater.pm

@@ -1281,6 +1281,11 @@ sub async_apply_config {
         $self->{gcode_preview_data}->reset;
         $self->{toolpaths2D}->reload_print if $self->{toolpaths2D};
         $self->{preview3D}->reload_print if $self->{preview3D};
+
+        # We also need to reload 3D scene because of the wipe tower preview box
+        if ($self->{config}->wipe_tower) {
+	    Slic3r::GUI::_3DScene::reload_scene($self->{canvas3D}, 1) if $self->{canvas3D}
+        }
     }
 }
 
@@ -1493,6 +1498,9 @@ sub on_process_completed {
     return if $error;
     $self->{toolpaths2D}->reload_print if $self->{toolpaths2D};
     $self->{preview3D}->reload_print if $self->{preview3D};
+
+    # in case this was MM print, wipe tower bounding box on 3D tab might need redrawing with exact depth:
+    Slic3r::GUI::_3DScene::reload_scene($self->{canvas3D}, 1);
     
     # if we have an export filename, start a new thread for exporting G-code
     if ($self->{export_gcode_output_file}) {