afk message improvements

[ldufr]

• [ ] Reduce spam by adding a timer between automatic reply.
• [ ] Make (x seconds ago) optional
• [x] Add something that confirm that afk message was set
• [x] Check for maximum message length when message is set.
• [x] Fix bug where you go back online directly when Automatically set Online... is enable after entering a afk message.
• [x] Add a way to remove the afk message.