FR: Add grouping display option to mail list panel

[gerroon]

Hi It would be very helpful if the grouping and ordering also has a presence in the mail listing panel because that is sometimes needed alot daily, sometimes looking at individual emails sorted by date is more important to understand what is going on than conversation, sometimes the otherway around etc.

Please see the image for a mockup.

https://i.imgur.com/zkWT0nQ.png

thanks