add account update contract.

Author: zhaohong

api/api.proto

@@ -25,6 +25,10 @@ service Wallet {
 
   };
 
+  rpc UpdateAccount (AccountUpdateContract) returns (Transaction) {
+
+  };
+
   rpc CreateAccount (AccountCreateContract) returns (Transaction) {
 
   };

core/Contract.proto

@@ -28,6 +28,12 @@ message AccountCreateContract {
   bytes owner_address = 3;
 }
 
+// update account name if the account has no name.
+message AccountUpdateContract{
+  bytes account_name = 1;
+  bytes owner_address = 2;
+}
+
 message TransferContract {
   bytes owner_address = 1;
   bytes to_address = 2;