Improve CmdFeature base class

Add default implementation of isEnabled() and add const

ApplicationLibCode/Commands/RicImportSummaryCasesFeature.h

@@ -62,7 +62,6 @@ public:
                                                                                                    const QString& pathCacheName );
 
 protected:
-    bool isCommandEnabled() override;
     void onActionTriggered( bool isChecked ) override;
     void setupActionLook( QAction* actionToSetup ) override;