Bump to API 3.0.0-ALPHA2 - READ DESCRIPTION!

Refactored level\format\generic\GenericChunk -> level\format\Chunk.
Re-added support for async chunk sending
Refactored most Level IO into new namespaces for more organisation
Removed LevelDB loader completely (will be re-added at a later date)

src/pocketmine/resources/pocketmine.yml

@@ -115,6 +115,8 @@ chunk-sending:
  #Save a serialized copy of the chunk in memory for faster sending
  #Useful in mostly-static worlds where lots of players join at the same time
  cache-chunks: false
+ #Use AsyncTasks for serializing chunks for sending.
+ async-chunk-request: false
 
 chunk-ticking:
  #Max amount of chunks processed each tick