[FIX] point_of_sale: prevent negative bank payments
[FIX] point_of_sale: use the same rounding sequence as the backend

Conflicts:
	addons/point_of_sale/static/src/js/models.js
Merge remote-tracking branch 'odoo/8.0' into 8.0
[FIX] Factor should be compared with factor, not id
[FIX] use inner join to avoid null id's in read_group
Merge remote-tracking branch 'odoo/8.0' into 8.0