Implement enum support in CachedSettingValue

Enums are stored as strings, that improves configuration file
readability and maintainability. String values are obtained via
QMetaEnum, and since with Qt 5.5 QMetaEnum::fromType() includes a
static_assert, this has to be a safe method.

src/gui/search/searchtab.h

@@ -31,7 +31,6 @@
 #ifndef SEARCHTAB_H
 #define SEARCHTAB_H
 
-#include <QVariant> // I don't know why <QMetaType> is not enought for Qt's 4.8.7 moc
 #include <QWidget>
 
 #define ENGINE_URL_COLUMN 4
@@ -44,6 +43,8 @@ class QHeaderView;
 class QStandardItemModel;
 class QVBoxLayout;
 
+template <typename T> class CachedSettingValue;
+
 class SearchSortModel;
 class SearchListDelegate;
 class SearchWidget;
@@ -59,13 +60,13 @@ class SearchTab: public QWidget
 
 public:
 
-    enum NameFilteringMode
+    enum class NameFilteringMode
     {
         Everywhere,
         OnlyNames
     };
 
-    Q_ENUMS(NameFilteringMode)
+    Q_ENUM(NameFilteringMode)
 
     explicit SearchTab(SearchWidget *parent);
     ~SearchTab();
@@ -106,6 +107,8 @@ private:
     static QString statusText(Status st);
     static QString statusIconName(Status st);
 
+    static CachedSettingValue<NameFilteringMode>& nameFilteringModeSetting();
+
     Ui::SearchTab *m_ui;
     QTreeView *m_resultsBrowser;
     QStandardItemModel *m_searchListModel;