Bitcoin-Qt: massive header and cpp cleanup

- try to enforce the same style to all Qt related files
- remove unneeded includes from the files
- add missing Q_OBJECT, QT_BEGIN_NAMESPACE / QT_END_NAMESPACE
- prepares for a pull-req to include Qt5 compatibility

src/qt/guiutil.h

@@ -5,6 +5,8 @@
 #include <QObject>
 #include <QMessageBox>
 
+class SendCoinsRecipient;
+
 QT_BEGIN_NAMESPACE
 class QFont;
 class QLineEdit;
@@ -13,7 +15,6 @@ class QDateTime;
 class QUrl;
 class QAbstractItemView;
 QT_END_NAMESPACE
-class SendCoinsRecipient;
 
 /** Utility functions used by the Bitcoin Qt UI.
  */