[C] Added Bukkit-4835: add fire fade example to BlockFadeEvent

#### Description:  
##### The Issue:
BlockFadeEvent was being called for fire fading (though not on inflammable blocks) but docs did not indicate such.

##### Justification for this PR:
Developers not aware of use of BlockFadeEvent on fire except by reading NMS code.

##### PR Breakdown:
Also modified javaDocs for BlockFadeEvent to add fire example.
 
##### Testing Results and Materials:

##### Relevant PR(s): 
 
C-1253 - https://github.com/Bukkit/CraftBukkit/pull/1253 - adds BlockFadeEvent for inflammable blocks  
 
##### JIRA Ticket: 
BUKKIT-4835 - https://bukkit.atlassian.net/browse/BUKKIT-4835