IgnitionHook for blocks set on fire by EntityLargeFireball

Closes part 2 of issue #32. Crow uses block status 7 for this, too,  but please check if it makes sense to break compatibility and use a new block status to be able to distinguish from small fireballs.
Merge pull request #34 from nosefish/patch-3

IgnitionHook for blocks set on fire by EntityLargeFireball