[bugfix] Make 'getcwd' function work for both Python 2 and 3, through

alias.

controlpanel.py

@@ -357,7 +357,7 @@ class ControlPanel(HasTraits):
         output = self.settings_file.edit_traits()
         if output:
             file_name = self.settings_file.file_name
-            if not file_name or file_name == os.getcwdu():
+            if not file_name or file_name == getcwd():
                 return False
             if not file_name[-5:] == ".json":
                 file_name += ".json"
@@ -514,10 +514,10 @@ class ControlPanel(HasTraits):
                 Item('enlargement_threshold'),
                 Item('growth_prefactor'),
                 Item('identity_signal',
-                     editor=EnumEditor(name='signal_names', cols=4),
+                     editor=EnumEditor(name='signal_names', cols=2),
                      style="custom"),
                 Item('growth_control_signals',
-                     editor=CheckListEditor(name='signal_names', cols=4),
+                     editor=CheckListEditor(name='signal_names', cols=2),
                      style="custom"),
                 Item('add_signal', show_label=False),
                 label="Model",