[C] Call EntityDeathEvent when Creeper explodes. Fixes BUKKIT-1812

**The Issue:**
The Javadoc for EntityDeathEvent states "Thrown whenever a LivingEntity dies"  However, at the current time, when a creeper explodes and kills itself, the event is not thrown, this is not consistent with the API description and therefore needs change.

**PR Breakdown:**
This PR simply adds a EntityDeathEvent call after a creeper explosion.  The handling of event set exp is there to counteract the lack of experience drops on the immediate death via Entity.die() as opposed to taking a more complicated route via changing the way a creeper dies during its kamikaze.   This can however be removed if you are so inclined.

**JIRA Ticket:**
https://bukkit.atlassian.net/browse/BUKKIT-1812