v0.1.3: Settings and Custom stimulation

Added an option panel, possibility to link all flicker to the same sequence

new type for flicker, Custom, where you have to choose a file that will contain the stimulation pattern.
that file needs to have the following format: a single line containing a list of float between 0 and 1 delimited by ';' eg: "1.0;0.3;0.6;0.4..." NO ';' at the end.
each of these numbers is the opacity of the window for the given frame in order.
the frequency option will disapear if you choose custom (it doen't make any sense anymore), but it still possible to give a phase (not functionnal right now)