Handle disconnecting peers

[pekam]

Currently, the component doesn't do anything with disconnecting peers. This causes following issues:

• The carets of disconnected users are still rendered.
• The state vectors contain entries that are no more needed (not a significant memory leak though, as the number of new connections should be relatively small in an editing session).
• The garbage collector (Garbage collecting the operation log #4) can't remove anything from the log after a user has disconnected, because it expects the disconnected client to integrate the operation before it can be removed.

There are a couple of options for this:

• Provide API for the users to handle this, as many real-time communication frameworks provide means for reacting to disconnecting peers. The problem is that this probably would mean that the user needs to interact with the internal client identifiers.
• Handle automatically when a peer hasn't sent an update for a while (considering the state message interval Send periodical state messages from inactive clients #5).