Improved Entity interface.

* Removed getPosition, getX, getY, getZ in favor of getLocation
* Removed getVectorRotation in favor of getRotation
* Removed EulerDirection in favor of Vector3f
* Removed interact methods as they are meant for Players
* Removed eject in favor of setPassenger
* Removed dismount in favor of setVehicle
* Renamed getRiding in favor of getVehicle
* Renamed getRidden in favor of getPassenger
* Renamed teleport to setLocation
* Renamed isDead to isRemoved
* Updated javadocs
Fixed NPE when dispatcher received no arguments.
Add PotionEffectBuilder.
Remove flags from setLocation, add getBaseVehicle
Rename isValid -> isLoaded
Merge pull request #290 from SpongePowered/feature/entities

Improved Entity interface.
Add API for force-loading chunks
Added BlockBreakEvent and ExpEvent.
Renamed ExpEvent to ExperienceEvent
Added support for BlockBreak, BlockPlace, BlockInteract events.

* Added BlockPlaceEvent
* Added BlockInteractEvent
* Added EntityBreakBlockEvent
* Added EntityInteractBlockEvent
* Added EntityInteractEntityEvent
* Added EntityPlaceBlockEvent
* Added PlayerPlaceBlockEvent
* Added PlayerBreakBlockEvent
* Added PlayerChangeBlockEvent
* Added PlayerInteractBlockEvent
* Added PlayerInteractEntityEvent
Merge pull request #303 from SpongePowered/feature/events

Added support for BlockBreak, BlockPlace, BlockInteract events.