Merge branch 'field-of-view' into develop

...ain/java/org/orekit/geometry/fov/CircularFieldOfView.java

...n/java/org/orekit/geometry/fov/EllipticalFieldOfView.java

src/main/java/org/orekit/geometry/fov/FieldOfView.java

...in/java/org/orekit/geometry/fov/PolygonalFieldOfView.java

src/main/java/org/orekit/geometry/fov/SmoothFieldOfView.java

...va/org/orekit/propagation/events/FieldOfViewDetector.java

...g/orekit/propagation/events/FootprintOverlapDetector.java

.../orekit/propagation/events/GroundFieldOfViewDetector.java

...java/org/orekit/propagation/events/VisibilityTrigger.java

...rg/orekit/geometry/fov/AbstractSmoothFieldOfViewTest.java

...java/org/orekit/geometry/fov/CircularFieldOfViewTest.java

...org/orekit/geometry/fov/DoubleDihedraFieldOfViewTest.java

...va/org/orekit/geometry/fov/EllipticalFieldOfViewTest.java

...ava/org/orekit/geometry/fov/PolygonalFieldOfViewTest.java

...rg/orekit/propagation/events/FieldOfViewDetectorTest.java

...t/java/org/orekit/propagation/events/FieldOfViewTest.java