CHIP-2021-05 Minimum fee rate voting via versionbits

This proposal, stimulated by recent discussion on lowering relay fees, would let miners adjust these relay fees via votes in the block header (versionbits).

A voting period of 1,008 block (~ 1 week) is proposed, with increases or decreases of 25% of the prior fee rate, but only if 75% or more of the votes are in favor of the increase/decrease. Otherwise the rate remains unchanged.

Relay fee is bounded between 1 sat/byte (today's rate) and 0.001 sat/byte, and hash voting can adjust the rate up or down within this interval.

You can find the full specification on GitLab: https://gitlab.com/freetrader/chips/-/blob/master/CHIP-2021-05_Minimum_Fee_Rate_Voting_Via_Versionbits.md

A discussion thread has also been opened on BitcoinCashResearch.org:

https://bitcoincashresearch.org/t/chip-2021-05-minimum-fee-rate-voting-via-versionbits/465

Review and feedback are much appreciated. Thanks!