Re-implement chunk sending, send chunks inside a radius instead of below a count
This sends chunks in concentric squares around players. When the radius is hit, it will pad out the radius until a full circle of chunks is loaded around the player.
TODO: implement radius-per-tick, send chunks in concentric circles, use radius for player spawning.
To set your server chunk radius, change `view-distance` in server.properties. Values are intended to be the same as MCPE render distance values. With matching client and server render distances the chunks should reach the horizon.
NOTE: You may notice significantly increased memory usage per player when increasing these values to something respectable. This is normal and expected.
A player with render distance 14 for example will cause loading of 600+ chunks. A player cannot however exceed the render distance limit set in server.properties - the server will simply not send any more chunks.
Render distance of 8 chunks is approximately 200 chunks. This is roughly equivalent to the original default max-chunks of 192 in pocketmine.yml, but sent in a circle instead of a square.
Wait for client to request a chunk radius before ordering chunks
Use 8 for default maximum radius (roughly matches old setting of 192)
Calculate spawn chunk count from chunk-sending.spawn-radius
* Added options to disable movement checks and anti-instabreak and API methods to control this
* Fixed anti-flight false positives
* Fix flight toggle kick cannot be disabled
* Added PlayerIllegalMoveEvent
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)
