Add support for icons + finished slider functionality + improved graph fluidity

-Icons are now displayed based on the element's type, and spacing has been adjusted so that icons and text no longer overlap each other
-Added preliminary icons to resources/; icons are taken from Cisco topology icons which are free to use but cannot be modified
-Graph parameters are generated using graph density heuristics instead of being hard coded, improving fluidity
-Slider now correctly scales icons and links (previous behavior only scaled text)
-Fixed a bug where address elements were displayed