Make getFilename() const

VirtualRobot/Obstacle.cpp

@@ -328,7 +328,7 @@ namespace VirtualRobot
     }
 
 
-    std::string Obstacle::getFilename()
+    std::string Obstacle::getFilename() const
     {
         return filename;
     }

VirtualRobot/Obstacle.h

@@ -113,7 +113,7 @@ namespace VirtualRobot
         virtual std::string toXML(const std::string& basePath, int tabs = 0);
 
         void setFilename(const std::string& filename);
-        std::string getFilename();
+        std::string getFilename() const;
 
     protected: