Bitcoin-Qt: add "send coins" to context menu in addressbook

- allows to directly select an address from the addressbook, chose "send
  coins" from the context menu, which sends you to sendcoins tab and fills
  in the selected address

src/qt/sendcoinsdialog.cpp

@@ -245,6 +245,26 @@ QWidget *SendCoinsDialog::setupTabChain(QWidget *prev)
     return ui->sendButton;
 }
 
+void SendCoinsDialog::setAddress(const QString &address)
+{
+    SendCoinsEntry *entry = 0;
+    // Replace the first entry if it is still unused
+    if(ui->entries->count() == 1)
+    {
+        SendCoinsEntry *first = qobject_cast<SendCoinsEntry*>(ui->entries->itemAt(0)->widget());
+        if(first->isClear())
+        {
+            entry = first;
+        }
+    }
+    if(!entry)
+    {
+        entry = addEntry();
+    }
+
+    entry->setAddress(address);
+}
+
 void SendCoinsDialog::pasteEntry(const SendCoinsRecipient &rv)
 {
     if(!fNewRecipientAllowed)