As a user, I would like islands to have a chance for treasure/resources to spawn on them

[zbostock56]

• Given that treasure/resources have spawned, the there may not be more than one item type per tile
• For every island, there is a chance that no items will spawn on the island
• Given that an item has spawned, the item will be rendered to the screen for the player to see and loot
• Given that items have been looted from an island, the island has a chance of spawning more as time passes
• Every island has a predefined capacity of items that it can spawn