[IMP] point_of_sale: remove empty payment lines when going back to product screen
[IMP] point_of_sale: confirmation message on session close when there are unposted orders
[FIX] point_of_sale: hr demo data products shouldn't be available in the point of sale by default
[MERGE] from trunk
[IMP] point_of_sale: rename Start Selling to Resume Session when appropriate
[MERGE] from trunk
[MERGE] point_of_sale: selected fixes from the trunk_review_pos branch