Change "hard fork" to "network upgrade" in EIPs documentation

[timbeiko]

As agreed to on the last AllCoreDevs call (see stream) and during the EIPIP meetings (notes), I've changed the term "hard fork" to "network upgrade" in EIP-1, the eips.ethereum.org index page, the repo README and for the upcoming upgrade, Berlin (cc: @axic).

The reasons for this change, as described on the call, were the following:

• "Hard Fork", while technically accurate, often is perceived by newcomers to Ethereum as to mean "chain split" (and possibly "free coins").
• Most previous HFs/upgrades on Ethereum did not result in a chain split, and using "network upgrade" does not bring this connotation to new users, so it should be used as a default, with the possibility of chain splits being explicit
• The EF has used "network upgrade" over "hard fork" for the past couple upgrades, see Istanbul, Constantinople.

On the last ACD call, it seem like there was agreement by core devs on moving this forward, modulo feedback on the specific wording. This is the place for that feedback 😄

Note: this does not remove previous instances of the term "hard fork" across the EIP repo/all EIPs. Only in the "guidelines" document and for the upcoming upgrade.

Ethereum Magicians discussion link: https://ethereum-magicians.org/t/using-network-upgrade-over-hard-fork-in-the-eips-repo/4255

[eip-automerger]

Hi! I'm a bot, and I wanted to automerge your PR, but couldn't because of the following issue(s):

• EIP 1 is in state Active, not Draft or Last Call
• File README.md is not an EIP
• File index.html is not an EIP
• EIP 2070 requires approval from one of (@axic)

[timbeiko]

It seems like there was a fair bit of opposition to this, documented on EthMagicians. After thinking more, I'm fine with keeping "hard fork" in the EIPs repo and having a soft norm of using "network upgrades" in more broad-reaching communications (like upgrade blog posts), which is the current status quo.