Chat thread with proof

[bourgeoa]

result of merging chat main (including message signature) and chat-threads.

This is nicely working with 2 remaining isssues related to send :

• no area to add a comment (send area) on a thread opened in the past (resolved)
• on same day you cannot add new comments. Send fails and you must reload the chat

[timea-solid]

If this is also containing the chat-thread branch, I guess we can close that one?