BSIP81: Simple maker-taker fees

[MichelSantos]

This initial PR contains 3 tests of BSIP81. At least 4 additional tests still remain to be completed.

This PR might need to be redone onto an alternate branch.

[MichelSantos]

It should be noted that there is a possible drawback to this implementation: after the hardfork, if an old client software submits an asset_create_operation, the asset will be created with a taker fee set to 0%. The asset owner can subsequently update the taker fee to something else with an asset_update_operation.

I consider that to be reasonable behavior but it can be altered with additional complexities if there is a strong objection.

[abitmore]

if an old client software submits an asset_create_operation, the asset will be created with a taker fee set to 0%.

Good catch. IMO the logic should be: if the owner didn't set a taker fee (old clients), then the old market fee rate applies to takers. It's an optional field, so it's not hard to distinguish between not set and 0.

[abitmore]

Created a pull request to update the specification: bitshares/bsips#271.

[abitmore]

Thanks. The code looks good so far, but perhaps there are conflicts when merging.
I haven't reviewed the test cases yet. Will do another review after it's labeled "ready for review".

[abitmore]

@MichelSantos please click "Ready for review"? Or you think it's still not ready for merge?

[dls-cipher]

I confirmed "ready" for review and will follow up with @MichelSantos. If anything is missing, he can push another PR.
@abitmore - please proceed with audit/review

[MichelSantos]

@MichelSantos please click "Ready for review"? Or you think it's still not ready for merge?

I was double-checking with some CLI tests. I think that it's ready for review.

[abitmore]

Thanks.

[abitmore]

The CI tests have passed. Looks like github has issues updating the CI status.

[abitmore]

Thanks.