add InitMessage() to noui and use debug.log for GUI

- this pull adds an InitMessage() function to noui.cpp, which outputs init
  messages to debug.log (this allows to remove some printf() calls from
  init.cpp)
- change InitMessage() in bitcoin.cpp to also write init messages to
  debug.log to ensure nothting is missing in the log because of the
  removal of printf() calls in init.cpp

src/qt/bitcoin.cpp

@@ -86,6 +86,7 @@ static void InitMessage(const std::string &message)
         splashref->showMessage(QString::fromStdString(message), Qt::AlignBottom|Qt::AlignHCenter, QColor(255,255,200));
         QApplication::instance()->processEvents();
     }
+    printf("init message: %s\n", message.c_str());
 }
 
 static void QueueShutdown()