[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.
[IMP] graph view on contacts
[FIX] sell future events only, not old ones
[IMP] Replace gantt chart library with dhtmlxgantt 3.1