Make graphical generation/output an option

[9600]

Running both LimeMon and LimeScan without any arguments results in execution and values output, then an attempt to display a GIF, which can result in error due to missing executables and/or graphics capabilities. E.g.:

SYSTEM("xdg-open output/outputRMS.gif") sh: 1: xdg-open: not found system() 32512 Resource temporarily unavailable

Propose that:

1. Default behaviour is not to generate a GIF
2. Make plot generation an option
3. Make displaying a plot after generating it another option

Most of the time these utils are likely to be used on headless systems, piping output to files and other processes.