Tidy up entity geometry stuff:

- Add a getCentre method for entities to GeometryUtils
- Replace getPositionEyes(0) with getPositionEyes(1) since it's more efficient, and by definition they must be the same
- Remove all the silly getEntityBoundingBox().minY stuff, this bug has been fixed since 1.8! (which begs the question: if it was considered a bug, how on earth did it go unfixed for that long?)
- A few other small things

src/main/java/electroblob/wizardry/util/BlockUtils.java

@@ -125,7 +125,7 @@ public final class BlockUtils {
 	 * is negative.
 	 */
 	public static IBlockState getBlockEntityIsStandingOn(Entity entity){
-		BlockPos pos = new BlockPos(MathHelper.floor(entity.posX), (int)entity.getEntityBoundingBox().minY - 1,
+		BlockPos pos = new BlockPos(MathHelper.floor(entity.posX), (int)entity.posY - 1,
 				MathHelper.floor(entity.posZ));
 		return entity.world.getBlockState(pos);
 	}