[FIX] Propate propagated_from_id when reconciling negative quants to the quant that loses it

When a negative quant is created but the positive quant counterpart is reconciling
a negative quant that of course also has a positive counterpart, the latter should eventually
let its field propagated_from_id tell that it originated from the very first negative quant as the
second negative quant will have disappeared through reconciliation.
[IMP] Rounding should be done on move immediately to default UoM and quants should be rounded to the default UoM
[FIX] Remaining qty should each time be in the default UoM of the product

Even with different UoM we want a consistent matching between moves and pack operations.
When calculating the remaining qty on move/pack operation we always start by converting the
qty on the move/operation to the default UoM and afterwards we subtract the links between them
which will also be in the default UoM of the product.
In order to create backorders / extra moves these quantities are used.