Added (get|set)_max_health, get_mob_effects, [set_]entity_onfire, play_entity_effect, play_sound, entity_death, updated player_death.

Yes, it uses a lot of the same code as player_death, which is because
that was made without using its own event. Next time effort is put
toward this, player_death can finally make use of its unique data.
Merge pull request #94 from jb-aero/master

Seven functions and 2 events.