The locale is a global state, and it was not properly reset to
whatever it was before the unitttest possibly changed it.
This is now fixed.
Not restoring the locale led to weird issues: depending on
the order chosen by "python -m unittest discover" to run
the unit tests, some tests would apparently randomly fail
due to the locale not being what was expected.
For example, test_period_in_timeperiod_archive would
call mock('posts/1970/ 1月/index.html',...) instead of
expected mock('posts/1970/Jan/index.html',...) and fail.
This dictionary is accessed by plugins (like `summary`) which add new
settings, so it should be public (i.e. no prefixed underscore).
The changed name length would have led to a re-indenting of the
default contents anyway, so I shifted them all to four spaces.
