[Istanbul] EIP-2200: Rebalance net-metered SSTORE gas cost with consideration of SLOAD gas cost change

[holgerd77]

Part of ethereumjs/ethereumjs-monorepo#501

Follow-up EIP to the failed Constantinople SSTORE EIP, see also #27 . There need to be some update to the price params respectively new params added, eventually named along the lines of PR #27 .

Should likely be addressed together with #61 in one combined PR (or at least released).

Update: Since EIP-2200 is still in heavy discussion it might actually be also make sense to handle and release separately.

[holgerd77]

Implemented in ethereumjs/ethereumjs-monorepo#581, will close.