Separate engine failures from thrust limiter

[bfrobin446]

As promised in issue #1, I got TestFlight's implementation of engine thrust loss working in OhScrap.

TestFlight has a class called EngineModuleWrapper that abstracts the differences between a base-game engine module and a RealFuels/AJE engine. I brought the entire class over instead of trying to pick and choose what parts of it were relevant to this change.

We now have three different ways for an engine to lose thrust:

• What OhScrap previously did with the thrust limiter: thrust decays by 10% every few seconds until it's effectively zero.

• Fuel flow drops by 50%, causing the engine to deliver 50% thrust until repaired.

• Specific impulse drops by 50%. The engine produces half thrust, but continues to consume as much fuel as it would at full thrust.

[zer0Kerbal]

Thank you! @bfrobin446 @severedsolo