Added option for additional ranking analysis.  

This adds option to add additional trackers to ranking analysis where ranks are computed normaly and additional trackers are then assigned ranks corresponding to their accuracy and robustness performance compared to normal trackers.

When dealing with tracker identifier understrike ("_") will create subscript for following characker in graph legend, which may look silly for e.g. xxxx_2013. I suggest using "-".  

Also in estimate_accuracy.m and estimate_failures.m there seems to be different format for results from year 2013. Instead of having [2] for failure, they have [NaN, NaN, NaN, -2].
This change was meant to be for users of the vot toolkit so they can test what would their tracker's rank be if it participated in the vot2013 challenge (without acctualy changing the 2013 results, what would normal ranking analysis do). I thought it would be appropriate to generate this code through template so the usage is as simple as possible. My next task is to write short tutorial for this piece of code for the vot website and having this code would be much easier.

Neverthless this code is outdated because we changed the <code>set_tracker_visual_identity</code>. Will you allow me to update this file or should i revert it back to default state?