M configHelpSourceEdit.py

1. Attach configHelpSourceEdit error dialogs to parent to avoid Tk root
   pop-ups.
2. Make configHelpSourceEdit OK button the default and bind <Return>.
3. Reformat configHelpSourceEdit.
4. ConfigDialog.SaveAllChangedConfig() had a bug which caused additional
   help sources to be deleted when other config items were changed.
4. Uniform capitalization in configDialog.
5. Update configDialog doc string.