config: give more fine-tuned sample hgrcs to this command The hgrc for user config is typically different from the hgrc at the system-wide or repository level. This patch provides different sample hgrcs for each level. Sometimes when copying repos around, the copy or the original don't have a default path yet, so at least for `hg config -l`, this ought to provide a more reasonable default and suggestions of what typically goes there. The actual sample configs go in the config.py file, to minimise clutter. In order to avoid an unnecessary import, the corresponding import for this dictionary is at the file level.