PluginContainer.getID() -> PluginContainer.getId().
Add GameEvent, child of Event, parent of game events.
Update CONTRIBUTING.md with formatting examples
Merge pull request #183 from jacklin213/temp

Update formatting examples in CONTRIBUTING.md
Add a message event and a command event.
Implement type/instance/snapshot scheme for blocks and entities.
Remove unused import from BlockVolume.
Make Entity implement Positionable, Rotatable again.
Add getX(), getY(), getZ() to Positionable.
Add getX(), getY(), getZ() to Block.
Add replaceData(data) to Block.
Add dummy vector factories.
Add a Direction enum.

This needs a unit test at some point.
Add Powerable interface and make Block extend it.
Make GameRegistry use Optional and update formatting issues.
Add basic support for biomes.
Move inventory subpackage to item.inventory.
Item -> ItemType.
Fix previous formatting issues with ItemType / Item.
Add Diggable interface and dig(), digWith() to Block.