Code review of [BSIP10] percentage based transfer fee

_From @abitmore on February 16, 2016 6:44_

As @theoreticalbts mentioned in https://github.com/cryptonomex/graphene/issues/570#issuecomment-184495783 I'm now creating this ticket.
- The BSIP10 feature requirement/description is [here](https://github.com/bitshares/bsips/blob/master/bsip-0010.md).
- My main develop branch is [here](https://github.com/abitmore/bitshares-2/tree/bts2-bts-transfer-fee) [here](https://github.com/abitmore/bitshares-2/tree/dev-transfer-fee).
- //Update: the branches below have been merged into the main develop branch (above)
- In [this branch](https://github.com/abitmore/bitshares-2/tree/bts2-bts-asset-update) I implemented a feature: with `asset_update_operation` the `new_options` can have a null `CER`, in this case `CER` of `asset_to_update` won't change. It addresses the No. 5 known issue in BSIP10. //Update: branch merged to main develop branch
- In [this branch](https://github.com/abitmore/bitshares-2/tree/bts2-bts-core-asset-update) I implemented a new operation `committee_member_update_core_asset_operation`, so committee can change some options of CORE asset. It addresses the No. 3 known issue in BSIP10. //Update: branch merged to main develop branch

@xeroc suggested me to re-base the code so he can merge it to test network easier, but I don't think it's good to do it right now, since it will cause loss of tracking to individual changes(I'm a bit bias here).

Current code is based on bitshares branch (the production branch). I may need to merge new codes from develop branch. Maybe need a new ticket for this? //Update: this job is finished.

_Copied from original issue: cryptonomex/graphene#583_

Start with the BSIP10 specification linked in the issue, then inspect the referenced dev-transfer-fee branch and the two related asset-update branches. Review the percentage-based transfer-fee implementation and its known-issue changes in the current develop branch. Done means producing a clear code-review decision or actionable findings; the issue does not name specific files or tests.

Written by the indexing model from the issue text.