Theming: Do not set the global palette

Setting the global palette is not a very good idea, because
it interferes with native styling.

On Windows 7 the dark theme was unuasable, because the text on
all natives controls was to bright.

All native controls and the global palette should be left alone.
Wherever we want styling/theming we have to use Manhatten style.

Change-Id: Ia1d0bfb190e4bde7be72f751afc0846570c1189d
Reviewed-by: hjk <hjk121@nokiamail.com>

src/plugins/coreplugin/coreplugin.cpp

@@ -130,7 +130,6 @@ void CorePlugin::parseArguments(const QStringList &arguments)
     Theme *theme = new Theme(qApp);
     theme->readSettings(themeSettings);
     setCreatorTheme(theme);
-    qApp->setPalette(creatorTheme()->palette(qApp->palette()));
 
     // defer creation of these widgets until here,
     // because they need a valid theme set

src/plugins/coreplugin/themesettings.cpp

@@ -435,7 +435,6 @@ void ThemeSettings::apply()
     {
         d->m_ui->editor->model()->toTheme(creatorTheme());
         QPalette newPalette = creatorTheme()->palette(qApp->palette());
-        qApp->setPalette(newPalette);
         foreach (QWidget *w, QApplication::topLevelWidgets())
             w->update();
     }