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.cpp

@@ -1,11 +1,14 @@
+#include <QApplication>
+
 #include "guiutil.h"
+
 #include "bitcoinaddressvalidator.h"
 #include "walletmodel.h"
 #include "bitcoinunits.h"
+
 #include "util.h"
 #include "init.h"
 
-#include <QString>
 #include <QDateTime>
 #include <QDoubleValidator>
 #include <QFont>
@@ -13,7 +16,6 @@
 #include <QUrl>
 #include <QTextDocument> // For Qt::escape
 #include <QAbstractItemView>
-#include <QApplication>
 #include <QClipboard>
 #include <QFileDialog>
 #include <QDesktopServices>