Synchronous communication interface with LockStep

[kaklik]

The actual implementation is limited by the update rate of the property tree available through the FG generic protocol. Unfortunately, the update rate is limited by the FPS rate of the graphics engine.

The graphics engine is unable to output regularly sampled data, the implementation is therefore limited to use no lockstep mode.

The FlightGear supports several other communication interfaces. The most promising is probably the HLA.