Previously to this, a level would be considered "not generated" if no level providers registered as valid for that directory. This caused astonishing behaviour when the user's world has, for example, a mixture of .mca and .mcr region files - the world would instead get _re-generated_ according to the default level format, which might or might not load the existing regions depending on the format used for generation. This behaviour is utterly absurd.
This changes the behaviour of the generated check to check for a non-empty directory in the given path. Non-empty directories without recognized world files in them are now considered to have an unknown format.
closes#2047
Since the player list already indexes players by UUID, it's simple to just use that for fetching the player.
A possible future improvement could be to allow fetching an _offline_ player by UUID, but no capability to do that is yet available.
This is completely unnecessary and adds extra complexity for no good reason. Maybe it was used historically, but nowadays it is only used to identify players to send async-prepared batch packets to.
There are two alternative ways to do that:
1. use spl_object_hash() as the targets array in CompressBatchedTask
2. use ServerScheduler's object storage to retain references to the Player[] array.
I've opted for the second method.
Removing these identifiers allows great code simplification in removePlayer() and removes the need for those old stupid hacks.
This also includes a backwards-compatibility break by removing the $identifier parameter of Server->addPlayer().
This cleans a lot of mess out of the bootstrap file, and also has the added bonus that threads which do not inherit functions can now get access to them by autoloading Utils.
Wanting initialized item factory does not require initializing the creative inventory. This is often useless and unwanted extra baggage (when this is used on threads for example).
Exceptions occurring early in the start sequence (before BaseLang is initialized) will result in the server hanging and not killing process as expected. This works around that issue.
This was causing new players to inexplicably spawn in the wrong place when joining a world for the first time which had a different level name than folder name. With LevelDB worlds, this caused them to spawn wayyyy up at y=32767 for no good reason.
The remaining methods, constants and fields in the NBT class now pertain to generic NBT functionality (except for the matchList()/matchTree() methods, but that's a job for another time). All NBT I/O specific logic has now been moved to NBTStream and its descendents.
This parameter is hardcoded to \pocketmine\PATH in PocketMine.php. Additionally, it does not make sense for the server source path to not be the server source path. \pocketmine\PATH is accessible from the Server context, therefore it should be used and does not need to be stored.
