[IMP] account/sale/sale_layout: standardization of Quotation/Sale Order/Invoice printed layout + add missing information

- Column alignment and order are now uniform across those reports.
- Display Due date on invoices.
- Display payment term and fiscal positions notes.
[ADD]Added stock_negative module to prohibit negative stock.

[IMP]Improved typo replaced OpenERP with Odoo.

[IMP]Removed sequence from openerp.py file.

[FIX]Fix yml test cases changed product_id..

[REM]Removed yml test case for negative stock.

[IMP]Improved yml test case.

[IMP]Improved yml test case.

[IMP]Improved yml test case.

[IMP]Improved yml test case.

[IMP]Improved yml test case.

[IMP]Improved yml test case.