Update MonoMac to latest (with a few tweaks)
Update InstanceWidget.Initialize to apply default styles if any
TabPage default constructor is needed for JSON for some reason.  Having a default value does not work.
Eliminate warning
Use Image instead of Icon for BaseAction/ImageMenuItem/ToolBarActionItem
Mac: Added new options to ToolBarItemHandler to use a button-style toolbar item, and convert image to grayscale if desired (using styles)
Added WidgetHandler.PostInitialize so that we can apply widget defaults after it has been fully initialized