Clean headers in Utils.

Forward-declare QGraphicsOpacityEffect in DetailsButton,
QProcessEnvironment in Environment, QFileInfo in fileutils,
QUrl in IWelcomePage, FancyLineEdit in PathChooser and
remove unneeded headers.

Change-Id: I7d5f273530dd2059bbdaf0899f0a3bc7e49e8482
Reviewed-by: hjk <hjk121@nokiamail.com>

src/plugins/debugger/qml/qmlinspectoragent.cpp

@@ -39,6 +39,7 @@
 #include <utils/qtcassert.h>
 #include <utils/savedaction.h>
 #include <QElapsedTimer>
+#include <QFileInfo>
 
 using namespace QmlDebug;
 using namespace QmlDebug::Constants;