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/sendcoinsentry.cpp

@@ -153,6 +153,12 @@ void SendCoinsEntry::setValue(const SendCoinsRecipient &value)
     ui->payAmount->setValue(value.amount);
 }
 
+void SendCoinsEntry::setAddress(const QString &address)
+{
+    ui->payTo->setText(address);
+    ui->payAmount->setFocus();
+}
+
 bool SendCoinsEntry::isClear()
 {
     return ui->payTo->text().isEmpty();