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/libs/utils/uncommentselection.cpp

@@ -28,11 +28,8 @@
 ****************************************************************************/
 
 #include "uncommentselection.h"
-#include <QtGlobal>
 #include <QPlainTextEdit>
-#include <QTextCursor>
 #include <QTextBlock>
-#include <QTextDocument>
 
 using namespace Utils;