[B+C] Add BlockFadeEvent for inflammable block fade. Fixes Bukkit-4835

#### Description:  
##### The Issue:
BlockFadeEvent not being called for fire fading on inflammable blocks.

##### Justification for this PR:
Could not prevent fire fading for most blocks (those that are not inflammable).

##### PR Breakdown:
Replaced world.setAir() with fireExtinguished call().
Also modified javaDocs for BlockFadeEvent to add fire example.
 
##### Testing Results and Materials:
Tested with my plugin AntiFire (http://dev.bukkit.org/bukkit-plugins/antifire/ and source at git://git.bukkit.org/minecraft/antifire/mainline.git), need beta 1.9 (https://dl.dropboxusercontent.com/u/3174158/AntiFire%201.9beta.jar). Verified that before fix, BlockFadeEvent is only called for flammable blocks, and that afterward, it is called for inflammable blocks. Specifically tested with (inflammable) grass blocks. 

##### Relevant PR(s): 
This should be links to accompanying PRs, or alternate PRs that attempted to perform the task.  Each reference should have a reason attached as to why it is being referenced (for example: "Similar to PR ### but won't empty your Bukkits").  Accompanying PRs need no explanation, but still need to be linked.
 
B-coming# - https://github.com/Bukkit/Bukkit/pull/#### - includes javadocs edit  
 
##### JIRA Ticket: 
BUKKIT-4835 - https://bukkit.atlassian.net/browse/BUKKIT-4835