Sale auto remove zero quantity lines

This module gives you a new option in the Sales settings: "Automatic Removal of Zero Quantity Lines". When it is turned on for a company, confirming a sales order will automatically delete any order line whose product quantity is zero, as well as any empty note lines (lines with no text).

• The setting is company-dependent, so each company can decide separately whether to use it.
• The option appears in the Sales settings screen, right after the online signature setting.
• When lines are removed, a message is posted in the order's chatter saying that some lines with zero quantities or empty notes were removed upon confirmation.
• The removal happens before the normal confirmation process continues, so the order is confirmed without those lines.

The module touches the sales order model (sale.order), the company model (res.company) and the configuration settings model (res.config.settings). It does not add new menus or reports; it only adds one checkbox in the existing Sales configuration screen and changes the behaviour of the Confirm button on sales orders.