Maik Hoepfel
44da815651
Stopped using null=True on CharFields
null=True is only useful for a few edge cases where one wants to
separate between '' and None. If null=True was found, it was removed.
If blank=True was not set already, it was set instead. If default=None
was set, it was removed (defaulting to '').
I then grepped the source code for tests 'is None' and 'is not None',
and checked the instances where default=None was set.
Fixes #584