Fixed Brake pipe pressure after coupling. When uncoupling the brakepipe pressure of all uncoupled cars is set to -1. Changed to set it to zero when coupling (so brake system works again).
Also removed some duplicate code when handling uncoupling.
git-svn-id: http://svn.uktrainsim.com/svn/openrails/trunk@323 a9f3cfff-6c41-7446-b0ca-052bd761e6eb