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/help/docsettingspage.cpp

@@ -75,7 +75,8 @@ QWidget *DocSettingsPage::createPage(QWidget *parent)
     m_ui.docsListWidget->addItems(m_helpEngine->registeredDocumentations());
     m_registeredDocs = false;
     m_removeDocs.clear();
-
+    if (m_searchKeywords.isEmpty())
+        m_searchKeywords = m_ui.groupBox->title();
     return w;
 }
 
@@ -126,6 +127,11 @@ void DocSettingsPage::apply()
     emit dialogAccepted();
 }
 
+bool DocSettingsPage::matches(const QString &s) const
+{
+    return m_searchKeywords.contains(s, Qt::CaseInsensitive);
+}
+
 bool DocSettingsPage::applyChanges()
 {
     QStringList::const_iterator it = m_removeDocs.constBegin();