message: implement xy-plane projection in standalone event display
diff: @@ -171,7 +171,7 @@ int InitGL() // All Setup For OpenGL Goes Here
  inline void drawPointLinestrip(int cid, int id, int id_limit = TRACK_TYPE_ID_LIMIT)
  {
  - glVertex3f(globalPos[cid].x, globalPos[cid].y, globalPos[cid].z);
  + glVertex3f(globalPos[cid].x, globalPos[cid].y, projectxy ? 0 : globalPos[cid].z);
  if (globalPos[cid].w < id_limit) globalPos[cid].w = id;
  }
  @@ -186,7 +186,7 @@ void DrawClusters(AliHLTTPCCATracker &tracker, int id)
  const int cid = tracker.ClusterData()->Id(tracker.Data().ClusterDataIndex(row, j));
  if (globalPos[cid].w == id)
  {
  - glVertex3f(globalPos[cid].x, globalPos[cid].y, globalPos[cid].z);
  + glVertex3f(globalPos[cid].x, globalPos[cid].y, projectxy ? 0 : globalPos[cid].z);
  }
  }
  }
  @@ -1013,6 +1013,7 @@ void PrintHelp()
  printf("[Z]/[U]\t\tShow splitting of TPC in slices by extruding volume, [U] resets\n");
  printf("[Y]\t\tStart Animation\n");
  printf("[G]\t\tDraw Grid\n");
  + printf("[I]\t\tProject onto XY-plane\n");
  printf("[X]\t\tExclude Clusters used in the tracking steps enabled for visualization ([1]-[8])");
  printf("[1]\t\tShow Clusters\n");
  printf("[2]\t\tShow Links that were removed\n");
  