Update of Magento stock quantity: reduced the memory footprint and improved...

performance by using read() instead of browse() and proceeding by steps of 1000
records at a time.

Bug report: https://code.launchpad.net/bugs/1330450
Original MP: https://code.launchpad.net/~camptocamp/openerp-connector-magento/7.0-update-stock-1330450/+merge/223393