Merge branch 'issue-833' into develop

src/changes/changes.xml

src/main/java/org/orekit/attitudes/AttitudesSequence.java

...timation/measurements/generation/EventBasedScheduler.java

src/main/java/org/orekit/files/sinex/SinexLoader.java

src/main/java/org/orekit/files/sinex/Station.java

src/main/java/org/orekit/forces/drag/TimeSpanDragForce.java

...ekit/forces/empirical/TimeSpanParametricAcceleration.java

...va/org/orekit/forces/maneuvers/jacobians/TriggerDate.java

...it/forces/maneuvers/trigger/AbstractManeuverTriggers.java

...orekit/forces/maneuvers/trigger/IntervalEventTrigger.java

...ekit/forces/maneuvers/trigger/StartStopEventsTrigger.java

src/main/java/org/orekit/gnss/antenna/AntexLoader.java

src/main/java/org/orekit/gnss/clock/RinexClock.java

...earth/troposphere/TimeSpanEstimatedTroposphericModel.java

src/main/java/org/orekit/propagation/AbstractPropagator.java

...ekit/propagation/analytical/BrouwerLyddanePropagator.java

...kit/propagation/analytical/EcksteinHechlerPropagator.java

...rg/orekit/propagation/analytical/KeplerianPropagator.java

.../org/orekit/propagation/events/PositionAngleDetector.java

...ianalytical/dsst/forces/AbstractGaussianContribution.java