remove channel_to_rex for Name Bids/PowerUp & RAM fees

[DenisCarriere]

Purpose

Currently all fees earned by the system contract are hardcoded and 100% of all fees are being directed to REX return pool.

By removing channel_to_rex and handling the fee independently per fee contracts, this allows for greater flexibility on how fees are being handled.

Feedback provided by

• @DenisCarriere
• @nsjames
• Tim Weston / Rob

Scope

• remove channel_to_rex from:
  • RAM buyram
  • RAM sellram
  • PowerUp CPU & NET powerup
  • Name bids runrex
• remove channel_namebid_to_rex from:
  • Name bids onblock
• Transfer fees
  • transfer PowerUp fees to eosio.fee
  • transfer Name bid fees to eosio.fee
  • transfer RAM fees to eosio.fee

Fee account receivers

system fee	receiver
Premium Names bids	eosio.fee
PowerUp fees (NET & CPU)	eosio.fee
Bancor RAM market fees	eosio.fee

Preconditions

• All system fee balances should be directed & remain in eosio.fee account.
• Channeling fees to REX should be opt-in based on eosio.fee contract logic configurations

Requirements

• Implement "Donate to REX" ACTON #118
• Implement eosio.fees CONTRACT #120

Note: changes should be pushed to Antelope Reference contracts https://github.com/AntelopeIO/reference-contracts

[DenisCarriere]

Implemented via AntelopeIO/reference-contracts#72