[ADD] Module which skips the invoicing stage of the Sale workflow if the order has no lines with value.
[IMP] Delivery Orders for Sale Orders with no value are now created with an Invoice Status of 'none'.
[REF] Refactor to make pep8-compliant.
[REF] Refactor __openerp__.py to make pep8-compliant.
Merge remote-tracking branch 'origin/rm7063-sale-zero-value-workflow'