DecimalField value is not converted correctly

[maxirobaina]

This is a regression bug in django-firebird 1.8
Django 1.7 has a in operations a convert_values method which convert the returned value from db driver to a representative python type (according with model field definition). In that implementation on django-firebird 1.7 a DecimalField was adpated to correct decimal format.
In django-firebird 1.8, with the new get_db_converters and convert_FIELDTYPE_value methods the decimal formating was lost.

Then, by example:

class ModelWithDecimalFileld(models.Model):
    price = models.DecimalField(max_digits=18, decimal_places=2, default=0)

If we have an instance with price = 1990.00

In django-firebird 1.7

>> obj = ModelWithDecimalFileld.objects.first()
>> obj.price
>> Decimal("1990.00")

In django-firebird 1.8

>> obj = ModelWithDecimalFileld.objects.first()
>> obj.price
>> Decimal("1990")