update QRCodeDialog

- remove unused #include <QDebug> and lblBTC label
- update Bitcoin input field to a BitcoinAmountField to allow Bitcoin unit selection
- use BitcoinUnits::format for the resulting amount parameter in the generated URI (always use BTC as per BIP21)
- move MAX_URI_LENGTH and EXPORT_IMAGE_SIZE to guiconstants.h
- add OptionsModel in AddressBookPage and use it in on_showQRCode_clicked() to pass it to QRCodeDialog
- add OptionsModel in QRCodeDialog to enable display unit updates
- add updateDisplayUnit() slot to be able to imediately update currently set bitcoin unit
- make all labels in the UI-file plain text
- resize dialog to match for an updated layout (fields are now stacked and new field)
- remove unused parameters from private slots
- only enable save button, when QR Code was generated
- show message when entered amound is invalid
- add read-only QPlainTextEdit field to output generated URI

src/qt/bitcoingui.cpp

@@ -357,6 +357,8 @@ void BitcoinGUI::setClientModel(ClientModel *clientModel)
         connect(clientModel, SIGNAL(error(QString,QString,bool)), this, SLOT(error(QString,QString,bool)));
 
         rpcConsole->setClientModel(clientModel);
+        addressBookPage->setOptionsModel(clientModel->getOptionsModel());
+        receiveCoinsPage->setOptionsModel(clientModel->getOptionsModel());
     }
 }