Release 0.6.9

Release 0.6.9

• external_ids plugin now adds Record.as_xmlid method
• bugfix: ensure thet record is present in cache on init of Record class
• bugfix: [json-rpc], if RPC method results in None, then there is no
  'result' object in response, so if there are no 'error' object, nor 'result',
  then suppose that 'result' is None, thus it is possible to deal with
  Odoo methods, that returns None as result via RPC