Add a simple user interface to the event display?

[lucabaldini]

Our event display is fairly minimal---a matplotlib canvas that gets distroyed and recreated when we press enter and move to the next event.

I have mixed feelings about bringing in huge dependence such as PySide or PyQt for this, but since matplotlib has some native support for simple widgets such as buttons and sliders, I wonder whether it would make sense to improve the ergonomics of the display by adding some interactive features in pure matplotlib. At the very basic level two buttons to move forward and backward in the input file, and maybe a text box to select a specific event would be a big win, I think. Or maybe a slider?

Since we are at it, it would be nice to have a subplot where we dump all the event information in text form?

@augustocattafesta and @starquino What do you say?