entry in tutorial file and image for tutorial 511_PolyVectorFieldGeneral

Former-commit-id: d3b3d2cd4908232f9b25944da10d81a15960c560

tutorial/511_PolyVectorFieldGeneral/main.cpp

@@ -177,5 +177,7 @@ int main(int argc, char *argv[])
   viewer.callback_key_down = &key_down;
   viewer.core.show_lines = false;
   key_down(viewer,'3',0);
+  std::cerr << " *** Press keys 1-9 to select number of vectors per point. ***" << std::endl;
+  
   viewer.launch();
 }

tutorial/images/511_PolyVectorFieldGeneral.png.REMOVED.git-id

@@ -0,0 +1 @@
+9a6cb4e375e2b9a94155e147f94dfe3684c23265

tutorial/tutorial.md.REMOVED.git-id

@@ -1 +1 @@
-d0e101aea39668e374ff776b29cdd79667b7d8bd
+53ad377a1784cd2dcde351c875dc43637aa730a9