Add module purchase_from_product_tree

During a demo for a potential customer, after showing all the great features of procurements/re-ordering rules/etc..., I had this simple question : is it possible to "simply" create POs from the list of products, by just looking at the stock levels ? I had to admit that this simple feature was not available (at least to my knowledge)... so I developed the module purchase_from_product_tree.

Extract from the module description:
This module adds a wizard on the product variants tree view to create new purchase orders. Some companies don't want to use the re-ordering rules to create purchase orders for some reasons (complexity, fast changes in demand, etc...). Some companies may prefer to look at their stock level and, from this analysis, decide which product variants they need to re-order. This module implements this scenario.