automatic axis in cmsCanvas and cmsDiCanvas

[lenzip]

When someone has to produce a long batch of plots, it is tedious to have to adjust the x_min, x_max, y_min and y_max, especially when one considers that this would be typically handled by ROOT one was to simply create a canvas calling the default constructor and drawing a histogram on it.
Could we have a cmsCanvas and cmsDicanvas constructor that does not set x_min, x_max, y_min, y_max, nameXaxis, nameYaxis and actually takes those from the first histogram that is drawn to the canvas?