Remove extra self param from store_preset call. (#381)

It looks like an extra "self" parameter was added to the store_preset call in the add_preset function.

This prevents add_preset from working.

lib/gui/presets.py

@@ -141,7 +141,7 @@ class PresetsPanel(wx.Panel):
         if not overwrite and preset_name in self._load_presets():
             info_dialog(self, _('Preset "%s" already exists.  Please use another name or press "Overwrite"') % preset_name, caption=_('Preset'))
 
-        self.store_preset(self, preset_name, self.parent.get_preset_data())
+        self.store_preset(preset_name, self.parent.get_preset_data())
 
         event.Skip()