[C+B] Implemented FusedExplosive interface for all fused entities. Adds BUKKIT-3962, BUKKIT-3905

There is currently no unified way to represent explosives with a fuse, and to get/set the fuse ticks.

Here is the implementation of a new interface, FusedExplosive, to represent such entities and to give a way to get/set the fuse.

Creepers, TNTPrimed and TNTMinecart are now implementing FusedExplosive, with everything that goes with it (isIncendiary flag, yield). The Creeper's fuse ticks had to be modified because it used a count up rather than a count down, which didn't fit in the interface. TNTMinecart also fires EntityPrimedEvent like normal TNT.
B-839 - https://github.com/Bukkit/Bukkit/pull/839 - Interface declaration

BUKKIT-3962 - https://bukkit.atlassian.net/browse/BUKKIT-3962
BUKKIT-3905 - https://bukkit.atlassian.net/browse/BUKKIT-3905
BUKKIT-4171 - https://bukkit.atlassian.net/browse/BUKKIT-4171