Switch to sync zlib with 512k chunks, adjustable compression level

[extremeheat]

• Switch to synchronous zlib with 512kb chunks, fixes an memory fragmentation related to async zlib in nodejs. Should also increase throughput by blocking event loop alot less. Related: Zlib compression needs to be sync websockets/ws#1369 , zlib deflate results in a memory leak nodejs/node#8871 - not really a "memory leak" as GC does trigger, but memory starts to fragment and will crash the process if too many things in are in zlib queue
• Customizable compressionLevel and batchingInterval in options
• Emit 'connect_allowed' to match nmp, emitted after server ping
• Fix minor race condition in player spawning