Remove trailing None on calls made to the Magento's API (PHP 5.4 compatibility)

When Magento is used with PHP 5.4+, the API may return errors if we send
API calls with None in the last arguments. So, we remove all the
trailing None from the arguments before sending.

See https://bugs.launchpad.net/openerp-connector-magento/+bug/1210775
Remove trailing None in the requests recorded for the tests

Since ccfe65c removes the trailing None on the requests sent to Magento,
the data recorded for the tests must not include trailing None.
When exporting a tracking number and the picking is not exported yet,
export it
Prevent to export the tracking number twice

When the tracking number was written after the picking has been set to
'done', but before the job to export the picking was executed, the job
that export the picking was exporting the tracking number, but another
job was created to export the tracking number as well.
Now, the picking' job only exports the tracking number if it was already
there when the picking was set to 'done' (because in that case, the
second job is not created).
Get the magento id using the binder, get the new id after the export
Add translation terms
Remove unused import
Merge pull request #16 from guewen/7.0-export-tracking

Corrections on the export of tracking numbers:
Merge pull request #28 from guewen/factorlibre-php54_compatible

Remove trailing None on calls made to the Magento's API (PHP 5.4 compatibility)
Prevent to create duplicate bindings on invoices

The correction made at becc1bf2 was not working because it was
doing a 'continue' on the inner loop but not on the outer loop.