[FIX] point_of_sale: fix the +10, +20 and +50 buttons
[FIX] point_of_sale: fix the +10, +20 and +50 buttons

Because we now correctly format numbers, we have to parse the number
strings with web.parse_value(), then calculate the new amount and then
convert them back to a correctly formatted number string.

bplancher/odoo,storm-computers/odoo,microcom/odoo,microcom/odoo,sysadminmatmoz/OCB,microcom/odoo,storm-computers/odoo,ygol/odoo,microcom/odoo,bplancher/odoo,laslabs/odoo,stephen144/odoo,sysadminmatmoz/OCB,hip-odoo/odoo,storm-computers/odoo,sysadminmatmoz/OCB,sysadminmatmoz/OCB,laslabs/odoo,dfang/odoo,stephen144/odoo,Elico-Corp/odoo_OCB,hip-odoo/odoo,dfang/odoo,hip-odoo/odoo,Elico-Corp/odoo_OCB,ygol/odoo,Elico-Corp/odoo_OCB,dfang/odoo,laslabs/odoo,stephen144/odoo,storm-computers/odoo,laslabs/odoo,stephen144/odoo,ygol/odoo,stephen144/odoo,Elico-Corp/odoo_OCB,ygol/odoo,microcom/odoo,storm-computers/odoo,ygol/odoo,sysadminmatmoz/OCB,storm-computers/odoo,bplancher/odoo,dfang/odoo,sysadminmatmoz/OCB,dfang/odoo,Elico-Corp/odoo_OCB,sysadminmatmoz/OCB,bplancher/odoo,ygol/odoo,Elico-Corp/odoo_OCB,ygol/odoo,laslabs/odoo,hip-odoo/odoo,laslabs/odoo,bplancher/odoo,dfang/odoo,stephen144/odoo,bplancher/odoo,hip-odoo/odoo,microcom/odoo,hip-odoo/odoo