Show last N trials in Raster mode

[JaneliaAPIG]

NOTE: This might already work. Should test/understand case where stimNumDisplayRange(2) is finite (as opposed to Inf).

Dario Campagner: "I would like to be able to fix the number of trials to be visualized in the raster window and that it updates online keeping  the total number of visualized trials the same (e.g. if I want to see 100 trials, when it gets to trial 101, I want to see from trial 2 to 101, then from 3 to 102 etc ). "