[Umbrella] Widget styling - review

[Piotrek Koszuliński]

This issue covers styling enhancements. It includes:

• #13818 - Allow to link widget style definitions, so applying one style might disable the other
• #13828 - Widget classes should be added to wrapper rather than widget element
• #13829 - Add class based on widget type to the widget wrapper

[Piotrek Koszuliński]

Last but not least - after removing a style from an object the styles combo is not updated. An old bug, highly visible now.

[Marek Lewandowski]

cc

[Marek Lewandowski]

The task is complete, with an exception of #13818 which got moved to 4.6.1 and is tracked separately.