Added cSignEntity into API, added cChunkDesc:GetBlockEntity().

This fixes both #228 and #347.
Exported cJukeboxEntity to Lua API.

Ref. #228
Added cNoteEntity to Lua API.

Ref. #228.
Fixed growing issue with crops.
Merge pull request #349 from SamJBarney/master

Fixed growing issue with crops.
cProtocol add SendExperience() and debugging
Merge remote-tracking branch 'upstream/master' into playerxp
Removed BlockEntities' constructors from the API.

Plugins shouldn't construct block entities, rather, they will query them either from the cWorld (while playing), or from cChunkDesc (while generating).
Debuggers: Added the BlockEntity test harness when generating chunks.
Re-added rose to items.ini.
APIDump: Removed the BlockEntity constructors' docs.
cRoot::SaveAllChunks() doesn't wait for the save (deadlocks).

Rather, it only queues the save task onto each world's tick thread.
Removed cBlockEntity:CreateByBlockType() from the Lua API.

Plugins cannot be allowed to create block entities, that would result in memory leaks.
Debuggers: Removed the old OnChunkGenerated code testing the cBlockArea writing.
cChunkDesc::GetBlockEntity() re-creates block entity when blocktype doesn't match.
APIDump: Documented cChunkDesc:GetBlockEntity().
added cProtocol function to pass xp to client
APIDump: Documented the cJukeboxEntity.
APIDump: Documented cNoteEntity.
APIDump: Documented cSignEntity.