Reverses direction of a relationship. Switches relation source with target.
 An example how to reverse a relationship:
 
 // We have an arbitrary element which represents a relationship.
 Element element = ...;
 // Relationship reversing should be wrapped with session create/close calls.
 SessionManager sessionManager = SessionManager.getInstance();
 sessionManager.createSession("Reverse relation");
 // Reverse the relationship.
 Refactoring.RelationReversing.reverseRelationDirection(element);
 // Close the session.
 sessionManager.closeSession();