Fixed checkstyle warnings.

src/main/java/org/orekit/errors/OrekitMessages.java

src/main/java/org/orekit/forces/inertia/InertialForces.java

...a/org/orekit/orbits/CartesianOrbitWithoutCentralBody.java

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

...propagation/integration/AbstractIntegratedPropagator.java

...org/orekit/propagation/numerical/NumericalPropagator.java

src/main/java/org/orekit/utils/AbsolutePVCoordinates.java