Combat/zombie logout + anti-duping overhall

This is to replace onkeydown event detecting Esc press since it could be bypassed with mouse button assignment.

Other benefits:

Instant Respawn and Abort button disabling. Old method is slow and uses horrid spawn method to spawn button disabling that could be bypasses with spamming Esc.

The condition of abort is checked even when the Esc menu is up. 

Added proximity detection that would not allow log out if there is another player within 6 metres (anti-backpack-duping-items-glitch)

Each rejected abort comes with a flashing message explaining why user is unable to abort.