Graphs

Adds pie chart graphs for:
- HDD count by size
- HDD combined capacities by size
- HDD count by vendor
- HDD combined capacities by vendor

 On branch graphs
 Changes to be committed:
	modified:   Ltt/Display.pm
	new file:   Ltt/Plotting.pm
	modified:   Ltt/Strings.pm
	modified:   README
	new file:   fonts/FreeMono.ttf
	new file:   images/hdd_cap_by_size.png
	new file:   images/hdd_cap_by_vendor.png
	new file:   images/hdd_count_by_size.png
	new file:   images/hdd_count_by_vendor.png
	new file:   images/logo.png
	modified:   json/constants.json