Stock picking reallocation

This module adds a way to spread the products of a transfer over several dates instead of shipping everything at once. On a transfer form you get a "Start reallocation" button (it becomes "Reallocation in progress" once a draft reallocation exists). It opens a pop-up where you set up to five dates and, for each product line, how much should go on each date.

• The first date is the original transfer's date; the other dates create new transfers, each linked back to the original one as a backorder.
• Quantities are entered per product and per date; the screen shows the demand and warns you if you allocate too much or too little.
• You cannot allocate less on the first date than what has already been done on the move.
• A move with several detailed lines cannot be reallocated.
• You can save the reallocation for later and come back to it; only one draft reallocation per transfer is kept, older drafts are cancelled.
• When the transfer is confirmed, any pending reallocation is cancelled.
• After reallocating, messages are posted on the original and the new transfers linking them together.

It works on transfers (stock.picking) and their moves, and adds the reallocation and allocation screens.