Hopeful fix for simulation freezing.
Fixed the assignment of SimManager.Instance.Gravity in the FlightEngineer Update method. The Gravity field now accounts for the vessel's altitude in addition to the main body's radius. The TWR (Current) and TWR (Throttle) displays now show TWR relative to the vessel's position, instead of just displaying the surface value.
Merge pull request #1 from jclapis/jclapis

Fixed TWR (Current) to account for vessel altitude
Compiled fix assigning gravity in FlightEngineer.
Changed update request to be non-blocking