Use proper GroupId when reacting to accepted invitations

Fixes #955

briar-android/src/main/java/org/briarproject/briar/android/blog/BlogControllerImpl.java

@@ -106,7 +106,7 @@ class BlogControllerImpl extends BaseControllerImpl
 			BlogInvitationResponseReceivedEvent b =
 					(BlogInvitationResponseReceivedEvent) e;
 			InvitationResponse r = b.getResponse();
-			if (r.getGroupId().equals(groupId) && r.wasAccepted()) {
+			if (r.getShareableId().equals(groupId) && r.wasAccepted()) {
 				LOG.info("Blog invitation accepted");
 				onBlogInvitationAccepted(b.getContactId());
 			}

briar-android/src/main/java/org/briarproject/briar/android/forum/ForumControllerImpl.java

@@ -85,7 +85,7 @@ class ForumControllerImpl extends
 					(ForumInvitationResponseReceivedEvent) e;
 			ForumInvitationResponse r =
 					(ForumInvitationResponse) f.getResponse();
-			if (r.getGroupId().equals(getGroupId()) && r.wasAccepted()) {
+			if (r.getShareableId().equals(getGroupId()) && r.wasAccepted()) {
 				LOG.info("Forum invitation was accepted");
 				onForumInvitationAccepted(r.getContactId());
 			}

briar-android/src/main/java/org/briarproject/briar/android/privategroup/conversation/GroupControllerImpl.java

@@ -108,7 +108,7 @@ class GroupControllerImpl extends
 					(GroupInvitationResponseReceivedEvent) e;
 			final GroupInvitationResponse r =
 					(GroupInvitationResponse) g.getResponse();
-			if (getGroupId().equals(r.getGroupId()) && r.wasAccepted()) {
+			if (getGroupId().equals(r.getShareableId()) && r.wasAccepted()) {
 				listener.runOnUiThreadUnlessDestroyed(new Runnable() {
 					@Override
 					public void run() {