Add casualty unloading from wrecks

Currently with ACE if unit falls unconscious inside the wreck (i.e. tank gets knocked out and blows up) it typically bleeds out since it's impossible to unload it.

This MR adds ACE action to all wrecks that permits to unload unconscious casualties if vehicle is destroyed, one person at the time. It effectively mimics 'Unload' action that is accessible on unit if it falls unconscious in the intact vehicle.