General Mac Notification Center Fix

[timfallmk]

Just creating this as a placeholder for specific Mac Notification center issues:

So far:

• Icon doubling and resizing
• No in-Atom notification override

[benjamindean]

@timfallmk Can you, please, provide a screenshot of notification?

[benjamindean]

@timfallmk Made an attempt on fixing "Icon doubling and resizing". Probably, contentImage property is the cause.