Polish the settings dialog.

Add a title label to the pages. Use QGroupBoxes throughout.
Extend SavedAction to work with checkable QGroupBoxes. Polish UI files,
use common layout for VCS plugins. Performance: Apply only visited
settings pages. Add search keywords.

Task-number: QTCREATOR-26

src/plugins/cpptools/cppfilesettingspage.cpp

@@ -243,7 +243,8 @@ QString CppFileSettingsWidget::searchKeywords() const
     QString rc;
     QTextStream(&rc) << m_ui->headerSuffixLabel->text()
             << ' ' << m_ui->sourceSuffixLabel->text()
-            << ' ' << m_ui->lowerCaseFileNamesCheckBox->text();
+            << ' ' << m_ui->lowerCaseFileNamesCheckBox->text()
+            << ' ' << m_ui->licenseTemplateLabel->text();
     rc.remove(QLatin1Char('&'));
     return rc;
 }