Moved MaxPlayers and Description from cWorld to cServer.

Also started creating a new cWorld::cTickThread class, but not used yet.
cIsThread: Added the Stop() method and debugging output in Wait()
Removed cServer::m_pState, dissolved into direct member variables.

The server tick thread is now in the cServer::cTickThread object.
Each world now ticks in a separate thread.
cIsThread threads get a window identification on Win.

This enables tools such as TaskInfo to report the thread name directly.
Added cWorld:QueueSaveAllChunks() function for saving chunks asynchronously.

The cWorld:SaveAllChunks() is therefore deprecated in the API and will be removed soon, use QueueSaveAllChunks() instead.
Merge branch 'master' into PerWorldThreads
Removed unused cServer::IsConnected() function.
Removed cServer::BroadcastChat() and cServer::SendMessage().

These two functions make it difficult to move to the new ticking system, and they aren't used anyway. If so required, they can be emulated by ForEachWorld / ForEachPlayer calls.
Fixed logging into debug console.

Was missing the LF at the end.
Clients are now ticked in cServer first, then in cWorld once they get assigned a world.
Merge branch 'master' into PerWorldThreads.

Also fixed the AllToLua script not resolving conflicts.
Updated the Core Lua files in MCServer project externals.
Exported cWorld:BroadcastChat() to the Lua API; used in the Core.
Player counts are now properly handled.

Fixes #80
Added mtilden to contributors list.
Fixed crashes in world's clientlist manipulators
Server counts the players correctly.

Was missing the PlayerDestroying() call, so players weren't removed from the playercount.
Updated CONTRIBUTING.md with basic recommendations
Fixed wrong names for some metas.

They were E_BLOCK_ instead of E_META_.