Provide info to moderators on how to terminate session

[stevenGravy]

What

When a user is connecting to a session give instructions how they can terminate the session. Press t for terminate. Having a method to choose the char combo to terminate would be nice. Also using a combo that requires two chars (ctrl-t). could be better.

How

Add as part of the session starting information on how to terminate a session.
Provide a configuration option on the char combo.

Why

Users may not know how to terminate a session. Also a t is easy to accidently press.

[stevenGravy]

The observer option to leave char c would also be helpful to print out.