Update specification and wording of BSIP 81

[abitmore]

It's found that the specification was not clear enough.
See also: bitshares/bitshares-core#2136 (comment)

[abitmore]

This pull request changes only implementation details, I think it doesn't require a re-vote.

[MichelSantos]

This does clear up the issue; thank you @abitmore. I also agree that the clarification maintains the spirit of the original BSIP.

[sschiessl-bcp]

Since we are touching this BSIP can we add the remark that market fee is enabled for the market fees to be taken?

This sentence is not true strictly, only if market fee flag is enabled (market fee can be set but flag disabled, correct?)
"Before the consensus upgrade, when an order buying that asset got filled, the amount [...] will enter the asset's market fee sharing process."

[abitmore]

To be honest I'm not a fan of spending time on tweaking the wordings. On one hand English is not my native language, on the other hand the spirit of the BSIP and the change is clear enough, the most important thing to put our efforts on is to push forward fast. The things didn't describe in the text is simply won't be changed. Since the system is already quite complex and it lacks of detailed documentation, IMHO this BSIP is not the best place to explain all the details and to finish all the docs. KISS.

Actually I already feel the "capped by max market fee" sentence is already annoying as we have to repeat it again and again but it's not the most important thing to focus on in this document, I'd rather avoid mention it at all. The "market fee sharing process" phrase is similar.

If I'm not getting productive help here, I don't mind to merge it without anyone else's approval.

[abitmore]

IMHO the "market fee sharing process" implies several things, one of them is "if the asset doesn't enable the charge_market_fee flag, no fee will be charged".

[sschiessl-bcp]

Sounds good. Update makes it clearer