Improve header for selecting all schema fields when dropping a schema

When drag and dropping a schema / complex field / property (not a widget) in Designer, it is not clear that the header allows to select all fields ( https://app.prodpad.com/feedback/61e68350-8ef5-11ea-8e51-4714006b5fa4/canvas )

AC

• Change styling so that the header appears like one
• Change button label to "generate"
• Validate the change with Randy