Add support for bech32 in genesis file

[ethanfrey]

Builds on #347

Also allow the bech32: prefix to be parsed:

We can use tendermint bech32 implementation as an example and use the implementation from https://github.com/btcsuite/btcutil/tree/master/bech32

We should also verify the library matches the values we have with iov-core (use some standard encode/decode test vectors)

[husio]

When importing a bech32 implementation I think we should test it ourselves as well to ensure the quality. We can probably copy tests from iov-core.
We have used https://github.com/ltcsuite/ltcutil in the past and the implementation was wrong. I have wasted time trying to find an issue in my code assuming that the bech32 implementation was correct.

@webmaster128 created a bug report for the tlcutil repository but I can see that they have solved the problem by disabling the issues 😂

[webmaster128]

@husio I think they don't care much about code they inherit from https://github.com/btcsuite/btcutil and don't use. Maybe it is worth fixing the btcsuite/btcutil implementation and use it.

[husio]

Blocked by btcsuite/btcutil#137 unless we will use different bech32 decoder implementation.

Initial work done in https://github.com/iov-one/weave/tree/bech32_support_issue_362

[ethanfrey]

Looks like that library is a no-go for now. I was digging in to see if the bech32 c utility was reliable (or maybe that one had errors). Seems this uses code pulled from the reference implementation.

Digging for test vectors to validate one over the other, I found a list of reference implementations in many languages, including go. And this version includes a complete test suite with test vectors.

Digging in, I found no license file, but as one github user pointed out, there is a BSD license in the source itself.

Given this code has not changed in around 2 years and is a reference implementation, I would suggest copying these files (including the original copyright notice) into our repo and using that.

[husio]

Copy https://github.com/sipa/bech32/tree/master/ref/go/src/bech32 as is into weave/crypto as weave/crypto/bech32.

[matheusd]

Decode() returns a slice where each element has 5 bits of the payload data. You need to further call ConvertBits to get the original data:

	// ...
	payloadDec, err := bech32.ConvertBits(payload, 5, 8, false)
	if err != nil {
		t.Fatal(err)
	}

	if !bytes.Equal(want, payloadDec) {
	// ...

[ethanfrey]

Thanks @matheusd

I was really wondering how this implementation could differ from the standard. I guess we have two approaches that work now.