This fixes things like:
  portal_catalog(source_reference={'query':'foo OR bar', 'key':'KeywordKey'})
or:
  portal_catalog(query=AutoQuery(source_reference='foo OR bar', key='KeywordKey'))

So we get:
  (`...`.`reference` LIKE '%foo%' OR `...`.`reference` LIKE '%bar%')

instead of:
  `...`.`reference` IN ('{\'query\': \'foo\', \'key\': \'KeywordKey\'}',
                        '{\'query\': \'bar\', \'key\': \'KeywordKey\'}')

Also, remove default values as it makes it easy for caller to leave arguments
out by mistake.
Also, use positional arguments as they are faster than named arguments.

See merge request nexedi/erp5!1698