Romania stock account tracing

This module enriches accounting entries with stock information so users can trace which stock operation produced each journal item.

On journal items (account.move.line) it adds stored references to the related stock move, picking, picking type, source location, destination location, product category and a valuation type text. These are filled automatically when the related invoice or bill is posted, and also when a stock valuation layer is linked to an invoice line.

On stock valuation layers it adds the picking, the picking type, a direction (Input or Output, based on whether the value is positive or negative) and an absolute value. A new pivot view on stock valuation layers lets users analyse quantity and value by accounting account, direction and valuation type; the standard valuation action now also offers tree, pivot, graph and form views.

On stock pickings it adds a computed total value of the valuation layers of their moves.

Business rules visible in the code: for refund invoices only returned moves are kept, otherwise returned moves are excluded; when a valuation layer is linked to an invoice line, the stock data is copied onto the invoice line and, if a synthetic counterpart line exists, onto the largest counterpart line as well.