Add async RPC queue and operation classes.

Add z_getoperationstatus RPC command.
Add z_sendmany RPC command (dummy implementation, does not send actual
coins).

src/wallet/asyncrpcoperation_sendmany.h

@@ -0,0 +1,32 @@
+// Copyright (c) 2016 The Zcash developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef ASYNCRPCOPERATION_SENDMANY_H
+#define ASYNCRPCOPERATION_SENDMANY_H
+
+#include "../asyncrpcoperation.h"
+
+#include "amount.h"
+
+#include <tuple>
+
+// A recipient is a tuple of address, amount, memo (optional if zaddr)
+typedef std::tuple<std::string, CAmount, std::string> SendManyRecipient;
+
+class AsyncRPCOperation_sendmany : public AsyncRPCOperation {
+public:
+    AsyncRPCOperation_sendmany(std::string fromAddress, std::vector<SendManyRecipient> outputs, int minconf);
+    AsyncRPCOperation_sendmany(const AsyncRPCOperation_sendmany& orig);
+    virtual ~AsyncRPCOperation_sendmany();
+    
+    virtual void main();
+
+private:
+    std::string fromAddress;
+    std::vector<SendManyRecipient> outputs;
+    int minconf;
+};
+
+#endif /* ASYNCRPCOPERATION_SENDMANY_H */
+