Add support for syncing blocked numbers

// FREEBIE

protos/IncomingPushMessageSignal.proto

@@ -52,11 +52,16 @@ message SyncMessage {
     optional AttachmentPointer blob = 1;
   }
 
+  message Blocked {
+    repeated string numbers = 1;
+  }
+
   message Request {
     enum Type {
       UNKNOWN     = 0;
       CONTACTS    = 1;
       GROUPS      = 2;
+      BLOCKED     = 3;
     }
     optional Type type = 1;
   }
@@ -70,6 +75,7 @@ message SyncMessage {
   optional Groups   groups   = 3;
   optional Request  request  = 4;
   repeated Read     read     = 5;
+  optional Blocked  blocked  = 6;
 }
 
 message AttachmentPointer {