Make ChatManager not to treat new sessions as stale ones
Some words about the attached bugfix: new chat sessions could be killed because the ChatManager periodically executes removeStaleChats.
The problem with this was, that it could be executed just in the same milisecond when a new chat session was created. In this case, the chat session had not yet a chance to join a group or to execute lastCheck. Hence, the ChatManager thought it was stale and removed it.
The bugfix gives newly created chat sessions some time to get in place before they are considered to be stale.
Patch does not cleanly apply, we can reopen if a new patch appears or a github pull request is generated.
Assigning to Daryl to commit.