Better If Group Widget Used Percentages

[Wajinn]

Group Widget can be hard to work with, because its proportions can be out of sync with children widgets that it contains, particularly for resizing.

Would be great if the Group Widget could work similar to the BoxLayout widget, where users could input percentages ("widget: (5%,10%) ++ (50%,25%)") for children widgets. This way their proportions would be easily consistent for any resizing.