[B+C] Added TNTIgniteEvent. Fixed BUKKIT-770

TNTIgniteEvent is fired when a TNT block turns into an entity (when it gets primed).
If it is cancelled, then the primed TNT isn't spawned.
Fixed formatting.
Documentation.
Moved TNTIgniteEvent to the entity event package, for diff visibility.
[B+C] Added FuseStartedEvent and TNTIgniteEvent. Fixes BUKKIT-770

There is currently no event fired when a TNT block is ignited, making it
impossible to link the TNTPrimed entities with the source TNT blocks.

FuseStarteEvent is a generic fuse event for all fused explosives, and should be
extended to TNTMinecart and Creepers (maybe with a new interface for fused
explosives).
TNTIgniteEvent is the specific event for TNT, to be able to get the source
block as well.

CB-1088 - https://github.com/Bukkit/CraftBukkit/pull/1088 - Implementation
Changed name to ExplosiveFuseStartEvent