Remote disconnection events should be handled correctly by CC computer and editor #52
Description
If the CC computer or the session server terminates the websocket connection, the editor doesn't know about it until it tries and fails to use the websocket connection, and vice versa.
If the websocket termination is intentional (e.g. the editor times the user out for inactivity, the user terminates the session by pressing E), then the editor and/or CC computer should be made aware of it using a special quit websocket message and handle it appropriately, instead of waiting for it to fail.