[MlMt] Better threaded view

[Max Rydahl Andersen]

Hi,

I made this layout (thank to Benny for help me fixing it :) that makes 
threading better IMO.

https://gist.github.com/maxandersen/10bc76e644848eb6944d

See screenshot to get idea on what it does: 
https://www.dropbox.com/s/t5gxgpjcg2aoqyb/Screenshot%202014-10-31%2011.01.06.png?dl=0

It adds a view that shows threads by relative date, who sent it and it 
shows not just by thread id as "thread" button does but also includes 
based on subject name.

For me this have been much better than the thread button which keeps 
"loosing" parts of threads for me.

Thus this threaded view is a pretty good compromise while we wait for 
proper thread grouping to be implemented :)

Thanks,
/max
http://about.me/maxandersen