tzinfo in DateTimeValidator

[rejoc]

Now that we can deal with tz aware datetimes in TG2/Ming, it would be great if tw2 DateTimeValidator accepts a tzinfo parameter

Something like

def to_python(self, value, state=None):
    if not value:
        return None
    try:
        return datetime.datetime.strptime(value, self.format).replace(tzinfo=getattr(self, 'tzinfo', None))
    except ValueError:
        raise ValidationError('baddate', self)