Add support for setting PNI-associated registration IDs and identity keys when changing numbers

service/src/main/proto/TextSecure.proto

@@ -41,6 +41,8 @@ message Envelope {
   optional uint64 server_timestamp = 10;
   optional bool ephemeral = 12; // indicates that the message should not be persisted if the recipient is offline
   optional string destination_uuid = 13;
+  optional string updated_pni = 15;
+  // next: 16
 }
 
 message ProvisioningUuid {