Adding support for rolltables as image sources

[Aedif]

• Rolltables can now be added as image sources via 'searchPaths' setting by using the following format:
  • rolltable:{rolltable name} (e.g. rolltable:GoblinVariants)
• Because of rolltables the same image path may now be assigned multiple names. Each of these names will appear as seperate images that can be selected in the ArtSelect pop-up and the TokenHUD side menu.