row spacing for circular fill (#2099)

lib/elements/fill_stitch.py

@@ -256,6 +256,7 @@ class FillStitch(EmbroideryElement):
            select_items=[('fill_method', 'auto_fill'),
                          ('fill_method', 'contour_fill'),
                          ('fill_method', 'guided_fill'),
+                         ('fill_method', 'circular_fill'),
                          ('fill_method', 'legacy_fill')],
            default=0.25)
     def row_spacing(self):

lib/stitch_plan/lock_stitch.py

@@ -1,10 +1,8 @@
 import re
-from copy import copy
 from math import degrees
 
 from inkex import DirectedLineSegment, Path
 from shapely.geometry import LineString
-from shapely.ops import substring
 
 from ..i18n import _
 from ..svg import PIXELS_PER_MM