[FIX]l10n_fr : Restore the appropriate accounts on tax ACH-19.6
[FIX] unit_price should be on other_pricelist
[REV] l10n_fr: revert changes to rev 8409
[FIX] product_visible_discount: don't change the behaviour of account.invoice to be consistent with the normal behaviour (don't use pricelists)
[FIX] product_visible_discount: don't compute negative discount, also prevent zero division
[MERGE] sync with 7.0
[FIX] product_visible_discount: for consistency reason with other modules don't use pricelist into account when creating invoice (only on SO/PO), don't display negative discounts as well (does not make sense) (opw #598290)