OS Statistics

Adds statistics on operating systems.

 On branch master
 Changes to be committed:
	modified:   Ltt/Digester.pm
	modified:   Ltt/Display.pm
	modified:   Ltt/Imaging.pm
	modified:   Ltt/Statistics.pm
	modified:   Ltt/Strings.pm
	modified:   json/constants.json
	modified:   json/systems.json
	modified:   ltt-rankings.pl
	modified:   ltt-rankings.txt