Order threads in a project based on activity #805

Currently threads are ordered based on datetime when they were started:

My suggestion is to by default order them by latest activity or allow switching between ordering behavior (thread created time / thread activity).
Now when i get back to some older thread, it's still kept at the position in the list where it was started and that makes it harder for me to orient in the project.

What to change:

• any new message in thread updates it's datetime for last activity to now
• add a way to order threads in projects by newest "last activity"