Added Conqueror Trait icon

Nothing too fancy, just a representation of a Mongol crown as depicted
in a few artistic representations of Genghis and subsequent Khans
Added Abdicated trait icon

Bonus! I already had an empty throne icon from some VIET work, so I made
it depressingly grey and added it; at the very least it'll work as a
placeholder if the trait ever gets put into the game
Merge pull request #148 from thefinestsieve/beta

Trait icons