[What] Revise the ChoiceNumberPanel has some white line

[Why] @CELL_SIZE is float number, the draw rectangle will have some truncate
[How] @CELL_SIZE store in integer

ui.py

@@ -34,7 +34,7 @@ def getChoiceNums(self):
         return sorted(self.focusNums)
 
     def setCellSize(self, size):
-        self.CELL_SIZE = size
+        self.CELL_SIZE = int(size)
         self.font = wx.Font( self.CELL_SIZE*0.5, wx.FONTFAMILY_DEFAULT, wx.FONTSTYLE_NORMAL, wx.FONTWEIGHT_BOLD, False, 'Comic Sans MS' )
 
     def setCellPos(self, i, j):