basically, an extensible tagged format.

note:
	db means a byte
	dw means a word (2 bytes here)
	dd means a dword (4 bytes here)

for starters, there's a header,
just in case some clutz decides to use this in AoS
	db "IceMap", 0x1A, 0x01

then a bunch of chunks follow in the format
	db "7 Chars", length
	
or, if the length is >= 255:
	db "7 Chars", 255
	dd length

the terminator is:
	db "       ", 0
yes, that's 7 spaces.

for AoS compatibility, the "header" CAN be at the end, BUT:
- MapData is NOT to be defined.
- all non-air blocks are assumed to be type 1.
- the map MUST be 512x64x512.

now, here are the defined chunks as per version 1 of the format.
	MapData:
		db "MapData", 255
		dd map_length
		dw len_x, len_y, len_z
		; map data goes here
		
		this contains the map itself.
		
		must appear exactly ONCE,
		or not at all if using AoS compat.
	
	MetaInf:
		db "MetaInf", length
		db field_name, 0
		db field_data, 0
		
		this contains meta info pertaining to the map.
		
		yes, there can be more than one MetaInf with the same name.
		
		defined names are:
			"*Name": name of this map
			"*Author": who made this map
			"*Tool": program responsible for making this map
		
		any custom names MUST NOT be prefixed with a *;
		this is reserved for OFFICIALLY DEFINED NAMES ONLY.
		
		all tools MUST leave "*Tool" fields intact.
		
		this field can appear many times.
		
		NOTE: THIS IS CURRENTLY NOT SUPPORTED AND SIMPLY IGNORED
		      BY THE ENGINE. But please include these if you can.
	
	MapEnts:
		db "MapEnts", length
		; entity data goes here
		
		this contains information regarding entities on the map.
		
		entity data is a JSON blob.
		
		entities include things like spawn points, pickup locations, etc.
		see format_icemap_mapents.txt for JSON format and known entity types
		
		must appear no more than once.