Remove compatibility with 10.4 from `tmprefs`
Format `tmprefs` according to `PEP 8`

#ignore
Modernize `tmprefs`

Make the following changes to update the function according to current
Python coding practice:

- Add documentation and doc-tests

- Use lower case notation for variables

- Use format strings instead of old % formatting

 #ignore
Add additional files to clean to cram tests

 #ignore
Remove local copy of `plistlib.py`