Fix possible stale p2p applications with no waiting timer running

[diederik]

When a contact does not respond to a P2P message, KMess cleans up the P2PApplication instance after a given timeout. There are some cases where the timer is no longer active. Those applications will be cleaned up when all switchboard connections to the contact close, but that could take too much time.

Steps to take

• Add a "last activity" time to every P2PApplication.
• Add a new task to the "idle" slot in ChatMaster to find stale P2P applications
• in P2PApplication::gotMessage(), detect if the timer is still active.
• If a P2PApplication did not have any activity for ~5 minutes, dispose it and report it's state at the console.
• Finally, fix those cases where the code had to clean up the P2PApplication.

[diederik]

note that KMess already aborts the sessions, just not too fast in my option. It's still a defect, but not too serious like something breaks really hard because of it.