Aliases:
	from a local file, kinda like requirements.txt, maps name to hash,
	either package/module name, or an author/public key name.

	This has to be treated specially.  If two aliases appear to be the same, but one is fetched a "secure" IPFS hash, it MUST be compared w/ what ever secure hash the two aliases had in common.  Otherwise a malicious package could "pretend" that it hash the sha256 that's the same, but provide a bad IPFS hash, and then we'd load the malicous package instead

Example:
from cas.a.jmg.utils import aiter, anext

Make sure that when an alias is used, that the same module is returned when a
direct hash import is used.

Local cache:
	if a directory like ~/.cas_cache exists, use it's contents automatically,
	and if it's writable, write any network fetched imported data to it.

Features:
	add:
		file
		url
		ipfs hash
		git(?)hub?

	init cache:

Loading resources from yourself (package):
	sys.modules[__name__] returns a valid module while your are being initalized, even for __main__, though may not work due to it not being a package, but probably can be emulated via __file__
	use importlib.resources: https://docs.python.org/3.7/library/importlib.html#module-importlib.resources
	> Loaders that wish to support resource reading should implement a get_resource_reader(fullname) method as specified by importlib.abc.ResourceReader.


Hash options:
	urn old ietf draft: https://datatracker.ietf.org/doc/draft-thiemann-hash-urn/
		- not up to date
	hash-uri: https://github.com/hash-uri/hash-uri
		- this looks best
	multihash: https://github.com/multiformats/multihash
		- no URI specification
	ipfs uri: https://github.com/ipfs/in-web-browsers/blob/master/ADDRESSING.md
		- not a hash, but useful for IPFS names
	ni: https://tools.ietf.org/html/rfc6920
		- complicated, not well supported