message storage and from removed from packedusermessage (weakness)

pb/messages.proto

@@ -30,6 +30,7 @@ message Invitation {
     string uuid = 6; // id that the friend gave you, that you should include to your reply to get recognized
     int64 expiry = 7; // the server allowed expiry date, it may be samller than the requested timeout according to server policy
     int32 step = 8; // progress in the inviattion process : 1=invite friend, 2=friend requests invitation, 3=friend's answer
+    string from=9; // used in step 3 the answer public key to check the signature in user message
 }
 
 
@@ -131,10 +132,9 @@ message ContactCard {
 // structure for sending a message to be forwarded to another user in protobuf format
 message PackedUserMessage {
 	string destination=1; // the peer's current conversation lookup public key
-    string from=2; // the sender public key
-    bytes payload=3;  // the message UserMessage encrypted with the destination peer's public key
-	bytes signature=4; // the payload signature with the client identity private key
-    repeated int64 serverTimestamp=5; // server time stamp, might be several in matriochka mode
+    bytes payload=2;  // the message UserMessage encrypted with the destination peer's public key
+	bytes signature=3; // the payload signature with the client identity private key
+    repeated int64 serverTimestamp=4; // server time stamp, might be several in matriochka mode
 }
 
 message ConversationStatus {