Move OpenSpaceEngine::isMaster method into WindowWrapper class

include/openspace/engine/openspaceengine.h

@@ -73,8 +73,6 @@ public:
     static bool isInitialized();
     static OpenSpaceEngine& ref();
 
-    bool isMaster();
-    void setMaster(bool master);
     double runTime();
     void setRunTime(double t);
 
@@ -249,7 +247,6 @@ private:
         
     } _moduleCallbacks;
     
-    bool _isMaster;
     double _runTime;
 
     // Whether the application is currently in shutdown mode (i.e. counting down the timer

include/openspace/engine/wrapper/sgctwindowwrapper.h

@@ -55,6 +55,7 @@ public:
     bool isRegularRendering() const override;
     bool hasGuiWindow() const override;
     bool isGuiWindow() const override;
+    bool isMaster() const override;
     bool isUsingSwapGroups() const override;
     bool isSwapGroupMaster() const override;
     

include/openspace/engine/wrapper/windowwrapper.h

@@ -175,6 +175,13 @@ public:
      * \return Whether the current rendering window is GUI-only
      */
     virtual bool isGuiWindow() const;
+    
+    /**
+     * Returns <code>true</code> if this application is the master for a clustered
+     * environment.
+     * \return Whether this applicaiton is the master for a clustered environment.
+     */
+    virtual bool isMaster() const;
 
     /**
     * Returns <code>true</code> if the current rendering window is using swap groups.