Add height and width options to set the dimensions of the output plot of an Omicron scan

Similar to what exists for omicron-plot!?

(...) plot-width=[plot width] plot-height=[plot height] (...) [plot width] plot width in pixels. By default, plot-width=850 [plot height] plot height in pixels. By default, plot-height=500 (...)

Increasing the "area" of a plot or changing the height/width ratio could be interesting, for instance for long scans (BNS or NS-BH candidates).