api.portal.get_localized_time() update (add support for datetime.date, add docs/tests)

Before the changes, get_localized_time() worked with DateTime and datetime.datetime, but returned None on datetime.date. Since zope.schema.Date uses datetime.date, I've added support for datetime.date (it ignores the long_format option and returns an empty string on the time_only option). 

I've also updated the docstring and tests (both were written as if only DateTime worked, so I've added the info and tests for datetime.datetime and datetime.date).

PS: Since the info in `setup.py` and `CHANGES.rst` still stated it's the 1.2.1 release, I also did the usual 'back to development (1.2.2dev) commit.