Added support for database maintenance. Added core plugin.

core/imetadataplugin.h

@@ -17,6 +17,8 @@ public:
     virtual QString pluginName();
     virtual QString pluginId();
     virtual QString pluginDescription();
+    virtual int schemaVersion();
+    virtual QStringList schemas();
     virtual void init(const QJsonObject &metaData);
 
 protected:
@@ -27,6 +29,8 @@ private:
     QString m_name;
     QString m_id;
     QString m_description;
+    int m_schemaVersion;
+    QStringList m_schemas;
 
     QString parseLocaleText(const QJsonObject &object);
 };