Created a utils package.

src/main/java/org/orekit/rugged/api/Rugged.java

...n/java/org/orekit/rugged/api/SensorMeanPlaneCrossing.java

src/main/java/org/orekit/rugged/core/BasicScanAlgorithm.java

src/main/java/org/orekit/rugged/core/IgnoreDEMAlgorithm.java

.../org/orekit/rugged/core/duvenhage/DuvenhageAlgorithm.java

.../java/org/orekit/rugged/raster/IntersectionAlgorithm.java

src/main/java/org/orekit/rugged/utils/ExtendedEllipsoid.java

...ava/org/orekit/rugged/utils/SpacecraftToObservedBody.java

...st/java/org/orekit/rugged/core/AbstractAlgorithmTest.java

...t/java/org/orekit/rugged/utils/ExtendedEllipsoidTest.java