Added: Missing cleanup of some contained references within various pooled classes.
Fixed: Jet engine simulation data is no longer included when IntakeAir deprived (i.e. in space).
Fixed: NullReferenceException when entering the flight scene within the FlightAppLauncher.
Fixed: Corrected an exception logging typo within the DisplayStack class.
Fixed: NullReferenceException within the DeltaVStaged readout upon exiting the flight scene.
Fixed: Flamed out engines are no longer perceived as active engines within the vessel simulation.
Removed: Redundant button enabled check within the FlightAppLauncher.
Removed: '?.' syntax sugar for easier compilation within non VS2015 IDEs.
