Added IntervalEventTrigger and StartStopEventsTrigger.

src/changes/changes.xml

src/design/continuous-maneuver-class-diagram.puml

src/design/maneuver-triggers-class-diagram.puml

src/design/propulsion-class-diagram.puml

src/design/small-maneuver-class-diagram.puml

src/design/small-maneuver-sequence-diagram.puml

...it/forces/maneuvers/trigger/AbstractManeuverTriggers.java

.../orekit/forces/maneuvers/trigger/FieldTriggerHandler.java

...orekit/forces/maneuvers/trigger/IntervalEventTrigger.java

...ekit/forces/maneuvers/trigger/StartStopEventsTrigger.java

...a/org/orekit/forces/maneuvers/trigger/TriggerHandler.java

...main/java/org/orekit/propagation/events/DateDetector.java

src/site/markdown/architecture/maneuvers.md

src/site/site.xml

.../triggers/AbstractManeuverTriggersInitializationTest.java

...rces/maneuvers/triggers/AbstractManeuverTriggersTest.java

...vers/triggers/IntervalEventTriggerInitializationTest.java

...t/forces/maneuvers/triggers/IntervalEventTriggerTest.java

...ers/triggers/StartStopEventTriggerInitializationTest.java

.../forces/maneuvers/triggers/StartStopEventTriggerTest.java