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/clientmodel.cpp

@@ -1,4 +1,5 @@
 #include "clientmodel.h"
+
 #include "guiconstants.h"
 #include "optionsmodel.h"
 #include "addresstablemodel.h"