Fireblight: Add legend for quantity icon shapes

src/main/webapp/map_applications/fireblight/icons/circle.png

...app/map_applications/fireblight/icons/circle_original.png

...main/webapp/map_applications/fireblight/icons/diamond.png

...pp/map_applications/fireblight/icons/diamond_original.png

...ain/webapp/map_applications/fireblight/icons/triangle.png

...p/map_applications/fireblight/icons/triangle_original.png

src/main/webapp/map_applications/fireblight/index.html