sim/time/sec

The newer JSBSim code has moved the property "sim/time/sec" to "simulation/sim/time/sec". All my models use at least one system which relies on sim/time/sec, so this breaks all of them. The effected systems are: alpha_buffet, beacon, beacon2 and crash-detect, and there may be others. I'll leave models in the Hangar as they are, which should work with FG 2.0. If you build a newer version of FG you'll probably have to edit the above files, or else FG will abort.