This addresses two types of introduction corner cases:

* force decline when two of our own identities are introduced to each
  other
* throw away introduction requests to the same identity
  (impossible to trigger from UI)

Closes #284

briar-api/src/org/briarproject/api/introduction/IntroductionConstants.java

@@ -57,6 +57,7 @@ public interface IntroductionConstants {
 	String ADDED_CONTACT_ID = "addedContactId";
 	String NOT_OUR_RESPONSE = "notOurResponse";
 	String EXISTS = "contactExists";
+	String REMOTE_AUTHOR_IS_US = "remoteAuthorIsUs";
 	String ANSWERED = "answered";
 
 	String TASK = "task";