[IMP] point_of_sale: sane multi order workflow + remove existing tooltips when we load the pos
[IMP] point_of_sale: remove hover effects, and change button colors when pressed instead (use :active) + tooltip removal was not always effective
[IMP] point_of_sale: forgot a few changes related to previous commit
[IMP] point_of_sale: this line doesn't make any sense and should never have been committed
[IMP] point_of_sale: removed the ScaleInvite Screen in cashier mode, + only update the weight value in ScaleScreen
[IMP] point_of_sale: big reworking of the scale screens: 
- no welcome scale in cashier mode, as it was an unnecessary delay for people who use it all day
- no more parallel calls to the proxy which could reorder or make the driver crash
- auto throttling of the proxy calls -> max 20 reads per seconds, but can go slower as well.
- faster and cleaner update of the weight in the scale screen
[MERGE] from trunk
[MERGE] point_of_sale: various fixes and improvements