Add modules stock_packaging_usability and stock_packaging_usability_ul

This contribution includes 2 modules that work together (that's why I put them in the same PR):
1) stock_packaging_usability: it restores the button "Put in current pack" which was native in v7 but is not present in v8, and it adds a button "Put residual in new pack" which puts all the lines that are not already in a pack in one single new pack

2) stock_packaging_usability_ul: it depends on the module stock_packaging_usability and extends it behavior: when you go "put in new pack" or "Put residual in new pack", it will ask you to choose a product.ul (logistical unit) that will be set on the new pack.