Added support for database maintenance. Added core plugin.

core/iplugin.h

@@ -5,6 +5,7 @@
 #include <QWidget>
 #include <QtPlugin>
 #include <QJsonObject>
+#include <QStringList>
 
 #include "service.h"
 
@@ -20,6 +21,8 @@ public:
     virtual QString pluginName() = 0;
     virtual QString pluginId() = 0;
     virtual QString pluginDescription() = 0;
+    virtual int schemaVersion() = 0;
+    virtual QStringList schemas() = 0;
     virtual void init(const QJsonObject &metaData) = 0;
     virtual QWidget *ui() {
         return m_ui;