Cleanup legacy contracts that are hindering the deployment process

[barrasso]

e.g.

• [ ] x
• [ ] SystemSettingsLib will not verify, but verify.js says it already is verified?
• [ ] Had to remove ProxyERC20 and ProxySynthetix from the list of contracts requiring ownership because it can’t accept a nomination twice.
• [ ] Mistakenly adds CollateralEth to the migrate contract.
  • Note: Maybe this is because of the index.js parameter mismatch? (ie. it was initially deployed with ISSUE_FEE_RATE: w3utils.toWei('0.001') but then later set to 0)

[cavalier-eth]

done (mostly)