samples: avoid using of legacy C-like API

- CV_RGB() macro is moved into opencv2/imgproc.hpp from imgproc_c.h
- samples/cpp/filestorage_base64.cpp is dropped

samples/cpp/fitellipse.cpp

@@ -207,7 +207,7 @@ int main( int argc, char** argv )
     }
 
     imshow("source", image);
-    namedWindow("result", CV_WINDOW_NORMAL );
+    namedWindow("result", WINDOW_NORMAL );
 
     // Create toolbars. HighGUI use.
     createTrackbar( "threshold", "result", &sliderPos, 255, processImage );