[IMP] point_of_sale: log pushed orders to the backend + disable proxy rpcs when the proxy is disconnected
[MERGE] from trunk
[IMP + FIX] point_of_sale: plugged the memory leaks
 - correctly call destroy on widgets
 - unbind backbone events on destroy
 - jquery show() hide() flooded jQuery.cache
 - introduced automated ui tests
[MERGE] from upstream
[IMP] point_of_sale: removed ProductWidget for faster product list updates
[FIX] point_of_sale: scaled product weren't ordered with the correct weight
[FIX] point_of_sale: missing renamings from the JobQueue refactor
[MERGE] from trunk
[MERGE] point_of_sale: various fixes and improvements