Add a basic stock managment system

[citorva]

To make stock managing efficient, it is useful to add a system which manages the quantity of each articles (if specified)

This system must add these following features:

• Add a form to add articles in the counter
• Automatically substract items when a sell is made
• Add a way to remove items when expiration date has been reached

[IraSkyx]

Agreed. FYI though this was an idea we had a while back, but ended up not doing it because of the cumbersomeness of syncing virtual with real stocks.
I think some work have been started in https://github.com/bde-isima/bde.isima.fr/tree/develop_nguyen