[ADD] stock_account: started code to record product.product prices changes.
[IMP] stock_account: started _get_value(location, product, datetime).

This should be replaced by a SQL view.
[IMP] stock_account: added view (maybe the subselect is wrong though) for the quant history.
[MERGE] main feature branch
[MERGE] main feature branch
[IMP] stock_account: removed useless test suite, changed the historization of cost price of products
[IMP] stock_account: standard price historization did it in my own way
[FIX] stock_account: return value in create() method
[IMP] wizard to get the stock valuation for a past date
[MERGE] main branch
[FIX] stock_account: give a list of ids to write()
[MERGE] main branch
[FIX] stock_account: fixed wrong implementation of default value for property fields
[MERGE] merged the branch with standard price of product historization and stock valuation at date report