Remove Directory Paths in Qt Classes Includes

Qt recommends that the path location not be used when including a class.
Also, this is how other files include Qt classes in the OpenCS app. This
change is for consistency only.

apps/opencs/editor.cpp

@@ -1,7 +1,7 @@
 
 #include "editor.hpp"
 
-#include <QtGui/QApplication>
+#include <QApplication>
 
 #include "model/doc/document.hpp"
 #include "model/world/data.hpp"

apps/opencs/main.cpp

@@ -4,7 +4,7 @@
 #include <exception>
 #include <iostream>
 
-#include <QtGui/QApplication>
+#include <QApplication>
 #include <QIcon>
 
 class Application : public QApplication