Added more unit tests for analytical orbit determination.

...st/java/org/orekit/estimation/EcksteinHechlerContext.java

...orekit/estimation/EcksteinHechlerEstimationTestUtils.java

src/test/java/org/orekit/estimation/KeplerianContext.java

...a/org/orekit/estimation/KeplerianEstimationTestUtils.java

...ion/leastsquares/EcksteinHechlerBatchLSEstimatorTest.java

...stimation/leastsquares/KeplerianBatchLSEstimatorTest.java

...imation/sequential/BrouwerLyddaneKalmanEstimatorTest.java