When a block is queried for retrieval we should add a check whether the
block falls within the frontier rules. If we'd always use `From`
retrieving transaction might fail. This PR temporarily changes
everything to `FromFrontier` (safe!).
* change gas cost for contract creating txs
* invalidate signature with s value greater than secp256k1 N / 2
* OOG contract creation if not enough gas to store code
* new difficulty adjustment algorithm
* new DELEGATECALL op code
This PR fixes a regression of the RPC where the default gas price that
was being used for transaction wasn't properly using the GPO. This PR
adds the GPO back to suggest gas prices rather than the hardcoded
default of 10000000000000.
Closes#2194
