Small comments in examples (and timing of marginals)

matlab/gtsam_examples/Pose2SLAMExample_graph.m

@@ -36,7 +36,9 @@ toc
 hold on; plot2DTrajectory(result, 'b-*');
 
 %% Plot Covariance Ellipses
+tic
 marginals = Marginals(graph, result);
+toc
 P={};
 for i=1:result.size()-1
     pose_i = result.at(i);

matlab/gtsam_examples/Pose3SLAMExample_graph.m

@@ -12,6 +12,8 @@
 
 import gtsam.*
 
+%% PLEASE NOTE THAT PLOTTING TAKES A VERY LONG TIME HERE
+
 %% Find data file
 N = 2500;
 % dataset = 'sphere_smallnoise.graph';