Add exercises for Rugged training; add RoughVisibilityEstimator in

src/tutorials/java/fr/cs/examples/DirectLocation.java

src/tutorials/java/fr/cs/examples/DirectLocationWithDEM.java

src/tutorials/java/fr/cs/examples/InverseLocation.java

...als/java/fr/cs/exercises/DirectLocationToBeCompleted.java

...a/fr/cs/exercises/DirectLocationWithDemToBeCompleted.java

...ls/java/fr/cs/exercises/InverseLocationToBeCompleted.java